zation of silver spaceships and the fascination of other worlds.

What is all this but time travel? Somehow, man is never satisfied with what he is. He always wants to go somewhere else, be something different. He imagines himself in another age, made more romantic by the gulf of time. It is not beyond belief that children of the future will amuse themselves by playing that they lived in that long-ago and wonderful period of the 1950's through which we ourselves are living.

Perhaps responding to this old fantasy of mankind, science fiction has long concerned itself with time travel as a major theme. Ever since H. G. Wells wrote the classic The Time Machine, writers have been having a lot of fun traveling through time.

It would be untrue, however, to present the idea of a time machine as anything but what it is, an intriguing literary device, part of the bag of tricks of the science fiction writer. We have no time travel in the sense of actually having a time machine at our disposal, and thus there is no such thing as a "science" of time travel. This is not to say that such a device is impossible; it is simply that we know nothing whatever about it.

The best we can do is guess.

Nevertheless, we need not be discouraged. There is a way we can travel through time, in fact as well as in fiction. The human mind is a time machine that can carry us backward or forward at will, and we have far more than guesswork to guide us in our travels.

Science fiction, like everything else in the world, has changed. In modern science fiction, the emphasis, the focus, of the story is far different from what it once was. It used to be, back in the days of Jules Verne, that writers were concerned with the all-important how. How could a ship travel from the Earth to the Moon? How could a man travel backward in time? This is still an important factor, but a new element has been introduced. The question today is not so much how the characters got where they were going, but rather what happened after they got there?

Many modern science fiction stories, in other words, start where the old ones ended. This is not to imply that the social sciences have replaced the physical sciences as a framework for fiction—surely with actual space flight almost upon us this is not the case—but simply that science fiction has acquired a new dimension. We still have our technology and our physics and our machines—but now we include human beings as well.

So it is that the real science in this book is not time travel at all. Instead, it is a science called anthropology.

II: What Is Anthropology?

A surprising number of people, if they have heard of anthropology at all, have only a confused impression that it has something to do with old bones and dinosaurs. There is some excuse for connecting it with bones, and none at all for dragging in the dinosaurs.

Anthropology is a rather large word, but it is nothing to be afraid of. Anthropology is the science of man, the science of you and me. As Dr. Clyde Kluck-hohn once phrased it, "An anthropologist is a person who is crazy enough to study his fellow man." More specifically, anthropologists concern themselves with groups of men and their cultures.

There are two main divisions of anthropology, physical and cultural. Physical anthropology concerns itself primarily with man as a physical animal—his skeleton, his race, how he is put together. Cultural anthropology deals with aspects of human behavior beyond the physical level—how do peoples live, how are societies put together, what do people do, and what have they done in times past. The further divisions of anthropology—ethnology, ethnography, applied anthropology and the rest—need not concern us here. In connection with this book, however, the division of archaeology should be mentioned. Archaeology is a part of cultural anthropology, and it is the study of the remains of man's material culture—his tools, his weapons, his pottery, his temples and homes—from its first appearance in time, and overlapping the period of reliable written records. Archaeologists dig up history out of the earth, history that was never written down.

There are no dinosaurs in anthropology, for the good and simple reason that anthropology concerns itself with man. Dinosaurs, despite certain comic strips to the contrary, lived many millions of years before the coming of the first man. So we will have to struggle along without the giant reptiles in this book, but they will not be missed.

Man himself is the most fascinating animal that ever existed on the face of the earth.

Anthropology is a young science, as sciences go, but it is a very important one. It is not merely a collection of odd facts about ancient times and quaint customs of the Indians. Rather, it is a technique that helps us to understand ourselves. In a world of atomic energy and warring nations, nothing is more important than learning to control and correctly utilize the vast forces that mankind has at its disposal. If we are to survive, we must first learn to understand. That is what anthropology is all about.

Ill: How Anthropology Is Used in This Book.

Science fiction writers are often guilty of extrapolation, but this is nothing to become unduly alarmed about. No extrapolationists have been investigated by the F. B. I., and they are not subversive in any way. When a writer extrapolates, he simply discusses the unknown in terms of the known. For example, no one of you now reading these words has yet lived in tomorrow, unless you have a time machine or two up your sleeve. Nevertheless, you could safely predict a number of things about that tomorrow that you have never seen. You could, for instance, predict that the sun would rise and you would have a better than fair chance of being right. You could go on and predict some of the things that would happen to you—you would go to school, or play baseball, or eat three meals a day, or go fishing down by the river. You have never seen tomorrow, but you can tell with some accuracy what your family will be like, how your family makes a living, what your beliefs and customs will be. This is extrapolation; you are discussing tomorrow in terms of yesterday and today. Inevitably, you will make some mistakes, but you will have a batting average that will be a lot healthier than one produced by mere wild guessing.

How is anthropology used in this book? Primarily by extrapolation, and this is how it works:

Most of what we know about the Neanderthals, or about the later Cro-Magnons, is based upon a relatively few anthropological finds. In some twenty sites in and around Europe, fragments of these people have been found—sometimes only a bit of jaw and some teeth, sometimes almost complete skeletons. Together with these skeletal remains, artifacts have been found, tools used by man.

The Neanderthals lived a long time ago; authorities disagree, as usual, about how long. However, they probably flourished roughly between 100,000 b.c. and 50,000 b.c. No man has ever seen a Neanderthal, and they left no written descriptions behind them. But we have a very good idea not only of what they looked like, but also of how they lived. From their skeletons, scientists have reconstructed their appearance, and these reconstructions have been both painstaking and convincing. There are details that we do not know, of course. For instance, skin color is something that cannot be determined from bones, and body hair vanishes with the passing of the years.

Chipped flint tools have been found with Neanderthal men, so we know a good deal about their weapons. Charred remains have been located, so the Neanderthals had fire. They buried their dead, and supplied the deceased with weapons for use in the hereafter. In one of the caves, a row of cave bear skulls was found, shaped like a shrine. Undoubtedly, the Neanderthals had a religion.

They lived as hunters, according to the evidence, killing and eating the animals of the Ice Age—notably the mammoth, the woolly rhinoceros, and smaller animals. This, in turn, means that they had a language of some sort. Hunting mammoths presupposes group activity, and group activity on that complex level demands a language.

We have small cause to look down upon the Neanderthals as stupid brutes. In fact, ironically, they had bigger brains than we have; some of them having a volume of about 1,625 cubic centimeters. The size of a man's brain, of course, tells you nothing about how good it was, but the Neanderthals, living as they did in the dawn of man, had a culture that commands respect. The mere accomplishment of survival for that long under those conditions is a very real achievement.

The Neanderthals are so named because the first recognized discovery was made in the little Neander gorge in Germany in 1856. "Thai" simply means "valley."

The Cro-Magnons were a different kettle of fish altogether. They were true Homo sapiens, who lived in Europe from approximately 50,000 b.c. until about 10,000 b.c. In this connection, it might be pointed out that there were no Neanderthals or Cro-Magnons in America at any time, so far as is known. Man evolved in the Old World, and the Indians who were living in the New World when the first settlers pushed westward had migrated here from Asia across the Bering Strait.

In general, we know almost the same things about the Cro-Magnons that we know about the Neanderthals. That is, we have their skeletons, their artifacts, and so forth. In addition, we have their paintings on the cave walls of southern France and northern Spain, the first great art produced by mankind. They were a gifted people, both physically and mentally, and they lived as hunters on the plains of the late Pleistocene, or Ice Age.

All this is of necessity very general, and suppose we now get down to brass tacks about the extrapolations in this book. This is a work of fiction, and does not claim to be anything else. However, I submit that the picture you will find here of Cro-Magnon man is not a fantastic one and is based on reasonable conjecture. Here are a few examples:

Language. There is no book that you can go to that will tell you anything about the language of the Cro-Magnons; they had no writing, and the spoken word does not last long. They had a language, of course, and probably a rather advanced one, but of what it may have consisted we do not know. Your guess, or mine, is as apt to be correct as any other. In naming the Cro-Magnons, I have simply tried to steer clear of the annoying "Ughs" and "Mo-Ros" that so often clutter up stories of this sort. There is absolutely no reason to suppose that Cro-Magnon names were on the level of animal grunts.

Social organization. Just as in the case of language, you cannot tell much about how a society was put together only by looking at a few bones. We do know, however, that the Cro-Magnons had a hunting economy. Therefore, I have pictured a social organization that fits in with what we know about other primitive hunting groups, such as the Plains Indians of our own country. That, incidentally, is the reason for the introduction of lean-tos into Cro-Magnon times. No such structures have survived, although certain house-drawings have been found on cave walls, but they probably existed. Hunting peoples must follow their game supply—any hunter knows that he cannot simply sit in one spot forever and kill enough game to live on. Caves are not portable, and just as the Plains Indians had their tipis, and the Eskimos their snow houses while on the trail, the Cro-Magnons must have had some similar shelter that they could carry with them.

Songs. Men everywhere have music and song, and I have given the Cro-Magnons a song to sing. We are prone to think of primitive peoples as somehow lacking in human values like laughter and song, but such is demonstrably not the case. I don't know any Cro-Magnon songs, and neither does anyone else. So I have invented one—but in so doing I have not just spun one out of the air, so to speak, but have instead reworked portions of an Indian prayer and a primitive chant into what I hope is a meaningful song. It is not suggested that this is a Cro-Magnon song, but simply that it might have been something like this.

The list could be extended indefinitely, but to little profit. I hope that these few examples have given you some idea of how the process of extrapolation works in this type of science fiction, and also shown you something of the differences between fact and fiction.

IV: A Bonus, Free of Charge.

This is a work of fiction, and as such its purpose is to entertain. If it gives you a few hours of pleasure, or even keeps you up all night to find out what happens, it has accomplished its mission. If it does not entertain, if it is not fun to read, then nothing else will make it worth your time.

If you do have a good time reading it, and I hope you do, that in itself is something. I also hope, however,

Mark Nye smiled and pointed at the dog. "You must have been feeding Fang some atomic-powered dog food," he told his uncle. "If we don't do something pretty soon, he'll tear the road apart."

Doctor Robert Nye took a battered pipe out of his hip pocket and filled it with tobacco from a can that had seen better days. "Fang's quite a dog," he agreed. "He's doing his level best to live up to his name."

As if to prove the doctor's point, Fang attacked a clump of grass viciously and yelped a challenge to the world in general. Lightning began to flicker in the mountains, and a distant rumble of thunder rolled down upon them from the hills. There was a faint smell of rain in the air and a cool breeze began to sigh across the valley floor.

Quite suddenly, two dark figures loomed up ahead of them on the road. Fang took one very short look at them and promptly abandoned his plans to be a great fighter. He dashed back to Mark at full speed and then, considering himself safe, tried a hesitant growl that proved to be magnificently ineffective.

As they drew nearer, the two figures proved to be Indians. They were of medium height, with straight black hair and dark eyes, and they were dressed in faded jeans and cotton shirts. Mark recognized one of them and waved a greeting.

"Howdy, Tino," he said. "Looks like we're about to get wet."

Tino paused. "Soon now," he agreed. "How does it go with you, Mark?"

"Fine, thanks—though I think you two scared Fang here half to death."

The Apache winked solemnly. "Injun scalpum," he said, imitating the strange dialect affected by the tourists when they talked to the Indians.

Doctor Nye and Mark laughed and waved good-by as the two Apaches moved along on their way to the near-by Mescalero reservation. It was almost dark now, and the evening was hushed with the threat of rain.

"A lot of history just walked by us then/' Mark said thoughtfully.

Doctor Nye puffed on his pipe and nodded agreement. "Tino is a member of a proud race," he said. "The blood that flows in his veins, the blood of the Mescalero Apaches, is the blood that goes back to Gion-na-tah, who finally had to surrender to his friend, Kit Carson —the blood that goes back to the warriors who fought with the great Victorio, back to the wily Nana, who at eighty years of age led fifteen braves against over a thousand soldiers, and back to the most famous Apache of them all—Geronimo."

Mark smiled. "We wouldn't have walked by them quite so easily seventy-five years ago. Not even Fang could have helped us much."

"The Indians were old when Rome was young,'* Doctor Nye mused, as the road began to rise into the hills. "There were Indians here in the United States when our ancestors in Europe still lived in caves."

When Rome was young. Mark felt his pulse quicken as the phrase fired his imagination. Out of the corner of his eye, he looked at the figure of his uncle walking beside him. He thought of his uncle's strange dream, a dream shared with him alone—would it ever come true?

Could they go back?

Rome, Imperial Rome. Visions of grandeur raced through Mark's head—visions made more vivid and real than ever by the secret he shared with his uncle. Rome in the days of the Caesars—a mighty city, hub of a fabulous empire, rich with glories that lived on still in the pages of history, that had never been forgotten. Rome with its seven hills, its mighty temples, its art and literature, its bloody games in the roaring Colosseum, now an empty ruin in modern Rome . . .

Rome—with the great figures of history walking its streets under a warm Italian sun. Julius Caesar himself, that wonderful, lonely man, and his adopted son, Augustus. Cicero, rich in eloquence, and the plotter Catiline, who heard the orations that spelled his doom. The twisted Nero and the mad Caligula. The curious and appealing Claudius—did he yet live, lost somewhere in the mists of time?

Could they go back?

The darkness was upon them now, and it was hard to see. Mark and Doctor Nye knew the road well, however, and proceeded without difficulty. The rain seemed to be suspended above them, waiting only for a trigger to loose a deluge. Flashes of lightning lit up the rocks and pines around them, and the booming of the thunder drew nearer as the road climbed into the hills near Ruidoso. Fang was very much subdued in the face of the storm, and kept tangling himself up in Mark's legs. Mark could smell the wet smell of rain around them.

"The Rome of the Caesars is closer than you think," Doctor Nye said quietly, sensing his nephew's thoughts. "Rome is only two weeks away."

Mark stopped short and then moved on again, his mind spinning with surprise. Two weeks? That meant—

"It's all finished," Doctor Nye went on, his pipe a red glow in the darkness. "I finished the actual construction last night, and all it needs now are a few final touches and supplies. Better brush up on your Latin, Mark."

"Hie, haec, hoc," said Mark, with a lightness that he did not feel. He knew how much this meant to his uncle. It was the result of twenty years of work, twenty years of dreams.

A machine to carry man backward in time—now a dream no longer!

The two walked on in silence, working their way back to Doctor Nye's mountain lodge. Mark could not help feeling a little in awe of the man who walked beside him. Doctor Nye had been father and mother to him ever since he was five years old, when his parents-had been lost in a plane crash. Doctor Nye, with no children of his own, had survived the disaster which had taken the life of his own wife, as well as of Mark's parents, and had been closer to Mark than to any other person in the world. Yet Mark felt strange beside him tonight, much as he might have felt walking beside Archimedes, Da Vinci, Edison, Einstein—or perhaps. Columbus, sailing into the unknown . . .

The unknown. What could be more mysterious, more wonderful, than a journey through time into the fabled past of Earth, that most incredible of all planets?

Doctor Robert Nye, who was a nuclear physicist working with the rocket experiments at near-by White Sands, had all his life been fascinated by the history of ancient Rome. The idea of time travel had been a hobby with him all his adult life, and he had pursued that hobby with the single-minded devotion and energy which men give only to their special dreams. Einstein's theoretical work on space-time had started him in the right direction, and the harnessing of the atom at Los Alamos had provided him a magnificent power source that enabled him to focus and direct the vast energies necessary to warp an organic substance back through space-time.

And now, at last, he was ready.

Mark Nye had seen Italy many times, on trips abroad with his uncle. He had seen Rome and had journeyed across the sea to North Africa where the genius Hannibal had threatened the Roman rule. He had traveled in France and Germany, where he had seen the sites of ancient man—which had fascinated him, just as the aboriginal lore of the Indians of the United States had always fascinated both Mark and his uncle. He had studied the past, and listened to Doctor Nye spin long and glorious tales about the past, and had even prepared himself to be able to accompany his uncle if his dream should ever come true—but now, actually to go . . .

The yellow outdoor light from Doctor Nye's lodge loomed up before them as they hurried up the drive. The storm was very close now, and they seemed to be walking along in the middle of a suspended island of nothingness, of electric suspense, where the rain could not reach them. Fang galloped ahead joyfully and camped by the front door, wagging the stump of his tail impatiently. Doctor Nye paused on the doorstep and squinted up into the darkness and the sighing of the pines.

"Looks like this will be some real weather, Mark." "Anything wrong?" asked Mark. "We have a lot of storms up here, and this doesn't look much worse than any of the others. It'll probably be over in an hour or so."

"Oh, I'm not worried about us," Doctor Nye said, tapping out the ashes in his pipe against his boots. "The house isn't likely to blow away or anything. I was just thinking—it's seven-thirty now, and with that storm all around us . . ."

"What's going on tonight? Something at White Sands?"

Doctor Nye nodded and scratched the impatient Fang's ears. "They were scheduled to test a new rocket tonight," he explained. "One of the Toney experimental jobs with a small atomic warhead. According to Jim Walls—you remember Jim, in charge of the rocket shoots—the rocket is supposed to go almost straight up, describe a short arc, and come down on a target a few miles away. But if it's storming like this in White Sands—"

"They'll probably call it off, if there aren't too many generals around," suggested Mark. "You wouldn't mind that too much, would you, Uncle Bob?"

Doctor Nye smiled. "You read my mind like a book, son," he said. "I'm due to fly my 'copter over there tomorrow to help Garvin make the radioactivity check, but if they call the shoot off we can work on our plans in the morning, and then maybe sneak off in the afternoon and see if we can't find some trout around here that aren't too smart for us."

Mark Nye brightened visibly at the prospect. "There are some swell places on the reservation," he said. "I snagged some beauties there last time, and the Indians invited me to come back and try it again."

"We'll keep it in mind," Doctor Nye agreed. "But first..."

"But first, open the door!" shouted Mark. "Here she comes!"

There was a sudden hush as the world seemed to pull its defenses together to ward off a mighty blow. Then a livid flash of lightning split the tops of the shuddering pines and a blast of thunder slammed into the earth like a monstrous fist of iron. A clean, fresh, wet smell blew up from the valley below and the first big, heavy drops of rain pattered like lead pellets on the roof of the lodge.

Doctor Nye threw open the door and they hurried inside, with Fang well in the lead and barking excitedly. Mark shut the door behind them and switched on the inside lights. The storm hit with full fury then, with the wind shaking the lodge and the rain pounding down in torrents on the roof.

"I'm just as glad we're not fishing now," Doctor Nye said. "You wouldn't be able to tell the fishermen from the fish."

Mark grinned. "I remember the last time we got caught out in a storm like this—I got so wet I didn't have to drink anything for a month."

The sitting room of Doctor Nye's lodge was neat and comfortable, with long shelves full of books, a bust of Caesar by the lamp on the table, Navajo rugs on the floor, and walls of lightly varnished pine. For a few minutes they were content just to sit there and listen to the storm raging outside. Fang had already found his favorite spot in the best armchair in the room and had gone to sleep.

"Well, who fixes supper tonight?" asked Doctor Nye.

"I will," Mark offered. "But before I do . . ."

"Yes?"

"You haven't let me go down with you to see the time machine since you started in on its final construction. You said I could see it when it was finished, Uncle Bob."

Doctor Nye nodded. "That's a bargain, Mark," he said, "though I'm afraid there isn't too much to see. If you're expecting some sort of weird contraption with electricity flying through the air all around it like in the Frankenstein movies, you're going to be disappointed."

"I'm not interested in what it looks like," Mark assured his uncle. "I'm interested in what it can do"

"Good boy," his uncle approved. "You get supper started and we'll have a look at my little brain child."

Mark disappeared into the kitchen, extracted the remnants of the previous night's roast from the ice box, and shoved it into the oven to warm up. Then he started a fresh pot of coffee and rejoined his uncle.

"Done," he reported.

Doctor Nye laughed. "Okay, Mark. Come with me."

While the storm roared around the mountain lodge and the rain turned the creeks into small rivers of foaming water, Mark followed his uncle down the steps into the special basement underneath the lodge. It was a rather ordinary basement, though filled with equipment and tools of a more complex nature than would be likely to be found in the average home workshop, except that the underground room was cut in two by a lead wall across the middle. Mark's heart pounded in his chest. The lead was a shield against radioactivity, of course, and that meant that on the other side of that lead wall. . .

backward trip in time had not yet been placed in the machine, it was virtually empty. There were no chairs. On one side of the sphere, opposite the power source, a control panel had been built up some four feet from the bottom of the machine.

Hanging from a projection in one wall was a belt holding a holstered .45 automatic. Mark Nye noted the gun with quick understanding. His uncle had carried the .45 in the First World War, when he had been an infantry captain. It had saved his life more than once, and he had kept the gun near him through the years, both as a sentimental good-luck charm and as a practical means of defense in a long and active life.

"So this is our time machine," Mark said finally. "It makes me feel so little . . ."

"That is because you don't understand it," Doctor Nye told him. He pulled out his pipe again, filled it with tobacco, and lit it. He blew a smoke ring at the control panel and smiled. "We always fear what we do not understand, Mark," he said. "I can't, of course, make entirely clear to you the physics and mathematics involved, but I can explain it more fully than I have before. It is essential that you understand what we are doing before we start out."

Mark sat cross-legged. "Fire away," he said.

"The idea of traveling through time has fascinated mankind for centuries," Doctor Nye began, puffing slowly on his pipe. His eyes had a faraway look in them, the way some men's eyes seem when they look at the stars. "It is customary to say that it has never been done, but that isn't true."

Mark looked at his uncle, wondering. Not true? But that could only mean—

"The point most people forget is that we are all time travelers," Doctor Nye explained. "Each and every one of us, every second of the day or night, travels through time. Even as I speak, I am moving forward in time, so to speak. When we came in out of the storm, it was seven-thirty. Now it is eight-fifteen. We have traveled forty-five minutes forward in time—into the future, if you care to look at it that way. In a sense, the world itself is a great time machine. We are all moving into the future, all the time."

"I never thought of it that way before," Mark admitted, feeling the lead sphere all around him, waiting ...

"But to go back into the past—to go from eight-fifteen to seven-thirty—that is something else again," his uncle continued. "That has never been done, as far as I know. But we'll do it, you and I! I know we can, and I know that it will be safe, or I would not consider taking you along. You're all I have in the world, Mark—all that matters to me. I would rather share this moment with you than with any friend I have, and I know you won't let me down. You've worked hard, you've learned a lot, and I know I can depend on you to do as I say. Even science has its human side, you know, and this is one dream that I do not care to share with anyone else."

Mark did not speak. . . . There were no words.

"Now then," Doctor Nye went on, "you understand that it is incorrect to refer to this device as a time machine. It is a space-time machine. What does that mean? Well, simply, it means that it moves through space as it moves through time. This is nothing really new. You know, if you'll stop and think about it, that space and time are hooked up together. They are both aspects of the same thing. You cannot move through space without moving through time as well—that is, you cannot go from New York to Washington in no time at all. In the same way, you cannot move through time without moving through space simultaneously. Even if you sit perfectly still in a chair and watch fifteen minutes tick off on a clock, you have moved many, many miles—for the earth is moving through space all the time, and our solar system and our galaxy are moving as well."

"I understand," Mark said. "That is what makes it possible for us to go into the machine here in New Mexico and come out in Italy, isn't it?"

"That's right," Doctor Nye agreed. "I have determined the exact relationship between space and time with respect to this machine of ours, and it will be possible for us to go from New Mexico to Rome in space while we are going from a.d. 1953 to 46 b.c. in time. One day, it may even be possible to travel through interplanetary space by the same means. That is, we might be able to arrange things so that we could go back millions of years in time and all the way to Mars in space—which might put us on Mars at a time when that planet held a high civilization."

Mark Nye's imagination ran wild at his uncle's words. Mars!

"Of course," said Doctor Nye, "the way the rocket experiments are shaping up it looks like we'll get to Mars easily enough without the space-time machine, but it's certainly something to think about." He drew on his pipe steadily, turning the air hazy with blue smoke. "Now," he continued, "what this machine actually does is to utilize the tremendous energies of the atom to warp space-time in such a manner that the machine can travel through them at will. But there are a few catches to all of this—a few conditions that you must remember. If you understand these, there is a great deal that would have seemed mysterious to you otherwise that will now be perfectly clear when we start out."

"I'm listening," Mark assured him. His heart was still beating rapidly with excitement. Here he was, sitting in the lead sphere in the basement of his uncle's home in New Mexico, in the year 1953. Vast energies were sleeping all around him, and yet at the touch of a hand, the flick of a switch, he would go where no man before him had ever gone—back, back past Columbus on his voyage to America, back past Marco Polo, back to ancient Rome two years before the death of Julius Caesar. Would they see him fall? Or could they perhaps prevent his death—warn him in advance of what was coming? What would happen then? What would the course of history have been if Julius Caesar had lived?

"First of all," his uncle said, "you must remember that this machine operates with atomic energy as a power source. The particular system that I have employed works on a principle of continuous nuclear reaction—that is, it is set to go a certain way before we start, and then once it is started it cannot be stopped until the space-time machine has reached its destination. There is no way to change the reaction once it has begun. It is like an automatic car that you have set to go to Detroit—once it starts out, you can't change your mind and go to San Antonio instead. Understand?"

"Clear so far."

"All right," his uncle continued. "The next thing to remember is that, for all its power, this machine is a very delicately balanced mechanism. You know how long and how hard I've worked, and most of the work involved was not in the theory or in the power source, but in the mechanism itself. Everything must balance exactly. I have finally gotten what appears to be the right combination, and of course I have kept detailed records, but whether or not I could ever build a duplicate space-time machine again, I don't know. Certainly, it would be the work of many years."

"I see," said Mark. "In other words, as far as we know, this is a once-only proposition."

"That's right. It isn't as though we had a device that would enable us to go backward and forward in time whenever we pleased. It will take us back and bring us home—once. I have picked Rome partly because I have been interested in it all my life, but also because it is relatively close in time—not over several thousand years away. For the first trip I think it wise that we do not attempt too much. Then again, we know a great deal about Rome, which will make it possible for us to conduct ourselves intelligently when we get there. We know the language, the detailed history, and the society and culture we are going into. We will know how to behave and take care of ourselves. It would be sheer and utter folly to attempt to journey into a time that we knew nothing about. We couldn't speak the language, we couldn't adjust to the life, we would be dressed in the wrong sort of clothing—everything would be against us. We'd probably wind up dead or in prison or in an insane asylum—if they had them!"

"How about the future?" Mark asked thoughtfully. "Could we go into the future?"

"I frankly don't know about the future," Doctor Nye said, puffing slowly on his pipe. "It's still an open question. Theoretically, I believe it could be done. But all the objections I have just raised would apply. We could not possibly know what we were going into, we could not prepare ourselves in any way. And there are other problems. Going into a future that does not yet exist is a risky business—for is it possible to change history, either of the past or of the future? What would happen to you, for instance, if you went back in time and killed your grandfather before your father was born? Time travel is full of unanswered questions. I do believe, however, that we'll find that it is impossible for us to alter history in any fundamental way. I believe that it would be wiser not to try to change things. Of course, there is the possibility of alternate time streams, multiple futures—"

"You're losing me now," Mark broke in. "We'd better stick to what I can understand or I may wind up being more confused than when we started out!"

"Okay, Mark, I'm sorry," Doctor Nye apologized. "Let's go back to fundamentals. There's just one more thing that you have to keep in mind—When the space-time machine reaches its destination and stops, it will be impossible for it to make the return trip right away. The balance of energies—the combination of forces-must have time to restore itself. The machine must have time to rebuild the energy potential in order to come back here to 1953."

"How long will that take?" asked Mark.

"Roughly two weeks—perhaps longer. We'll have to wait and see. Come here a moment."

Mark got to his feet and followed Doctor Nye over to the control panel on the side of the sphere. There was a bank of lights along the top of the panel and a carefully calibrated dial in the center. On each side of the dial there was a large knife switch with a black handle. Both switches were open.

"Careful now," cautioned Doctor Nye. "Don't touch anything—this baby is all ready to go. You'll notice that the controls are quite simple, and there's nothing mysterious about them. That green light burning there means that the machine is in order and prepared for operation. When the machine starts, the green light goes off and the red light comes on. When that red light is on, you must not try to change anything or the whole machine will explode. Don't forget that. Finally, when the machine stops, the yellow light goes on. That means it is safe to go out, but the machine is in the process of rebuilding the energy potential and cannot be moved. When the energy potential has been built up again, the yellow light goes off and the green light comes on again."

"That's clear enough," Mark said. "I suppose that the dial in the center is to fix the machine's destination?"

"Check," said Doctor Nye. He took the turning knob of the dial carefully between his thumb and index finger. "You see that the pointer of the dial is now set for 1953, and that the very fine small pointer that looks something like the large second hand of a watch makes it possible to set the machine for a specific day—even a specific minute and hour. Now, I turn to the dial—"

Cautiously, Doctor Nye turned the knob. Mark heard a series of faint but precise clicks. He watched the dial swing back across the centuries, back—

"There we are," said Doctor Nye. "It's now set for

46 b.c. and all I would have to do to get us back there would be to throw that left-hand switch. I don't have to tell you of the work it took to adjust the actual time spans to the calendar times. You know, of course, that the calendar has been often adjusted; by Gregory and Julius Caesar himself among others, in order to make it correspond to the actual lunar and solar years. But it is all integrated in this machine, and allowances made for such things. We can go back almost anywhere, and any time, just by twisting this dial—thus!"

Smiling, Doctor Nye pressed a release button and gave the dial a hard spin. A slight whirring noise filled the machine. After a moment, he engaged the mechanism again and there was a rapid series of clicks that slowly diminished in speed until there was silence.

"There we are," Doctor Nye said. "The machine is now set for—"

Suddenly, unexpectedly, there was a loud, urgent ringing from outside the sphere. Mark jumped slightly and then recovered himself. The space-time machine, he decided, was no place to hear sudden noises!

"That's the upstairs phone," Doctor Nye said quickly, a worried expression on his face. He glanced at his watch. "It's not quite nine o'clock—something must have gone wrong with the rocket at White Sands. Hold on, Mark—and don't touch anything."

Doctor Nye hurried out through the circular door and Mark heard his feet on the stairs as he ran up to answer the phone. He looked around him at the dull lead sphere. It was very quiet. He felt a slow, icy cold begin to creep up his spine.

Mark shivered. He was alone in the space-time machine.

Alamo—and by his side Napoleon and Genghis Khan. There stood Machiavelli and in the shadows, blind Homer sang an immortal song. There was Alexander the Great—there Socrates. David, Moses, Tutankhamen—all still lived and loved and dreamed. And beyond them, as in a cloud of blue smoke, the first men walked through the mists of dawn. Cro-Magnon, Neanderthal, Pithecanthropus—and farther still, lost in the haze of time, the dragons hissed and screamed across the face of the earth as the great reptiles—Brontosaurus, Stegosaurus, the fierce Tyrannosaurus Rex-plodded through the swamps at the beginning of time . . .

With a visible effort, Mark looked away. He still did not dare to move—he was taking no chances on being thrown by some accident into the time stream alone. When Doctor Nye, with his wide knowledge and calm self-assurance, was with him it was all right and everything was under control, but alone it was a different story. Mark stood very still, waiting for his uncle to come back.

It was very still now in the lead sphere of the space-time machine. It was so quiet that Mark thought that he could hear his heart beating in his chest. He swallowed hard, ashamed of his nervousness. He clenched his fists tightly, afraid of he knew not what. It was almost as if—

With a suddenness that numbed his brain, it happened. A slugging, hammering concussion slammed into his body and threw it across the sphere. A sharp, blasting roar boomed through the little room, and Mark felt the house shuddering around him. With desperation, Mark tried to keep his footing.

The rocket, the rocket, his mind screamed in the chaos. The rocket's gone off her course and blown up in the hills!

Swaying, stunned, Mark felt himself going. He fought valiantly not to fall, but his mind was spinning, his legs wobbled, and he sank toward the side of the sphere, falling, falling . . .

Too late, he saw that he was collapsing on the control panel. The tiny green light looked at him, laughed at him, pulled him down. Mark gasped breathlessly and tried to arch his body back away from it. It was no use. With a shudder he sank down against the control panel—and felt a knife switch click shut under his body.

Mark screamed once and tried to claw his way up again. It was too late. Horrified, his mind reeling with shock, he saw the green light wink off. The circular lead door of the space-time machine hissed into place, sealing him in. The red light in the control panel flicked on and a vast humming vibration filled the sphere.

The machine, his mind whispered. It's started—I'm trapped . . .

Mark couldn't get up and he dimly realized that he could do nothing even if he could get to the controls. Once the space-time machine got underway, it could not be tampered with. He was alone—going backward into time! Backward to—where?

Where was the machine set for? When Doctor Nye had spun the dial, where had it come to rest? Where was he going?

Desperately, Mark made a final effort to regain his footing. He pulled himself to his knees and felt the blood rushing and pounding in his brain. He gasped with shock and fought to get up. The pounding in his head became a roar—a roaring torrent of darkness that swirled and eddied and wrapped itself around him, pulling him down, down into the cool depths, down.

With a low moan Mark lost consciousness and slumped to the floor of the space-time machine.

As in a dream, sounds and faces swam before him. Fang dashed down a dusty road, barking excitedly. The two Apaches marched by under the gathering storm. The bust of Caesar stared at him with eyes of flame. His uncle shook his head, and his voice drifted up out of nothingness: "It would be sheer and utter folly to attempt to journey into a time that we knew nothing about . .

Mark Nye came to with a start and looked around him. Panic raced through his body, but he fought it down. This was no dream—that was certain. He was in the lead sphere, and the humming vibrations still buzzed in his ears. A gray atmosphere seemed to fill the space-time machine, and there was the feel of electricity in the air. The red light in the control panel was still on, and its flickering rays pushed out with a pinkish glow into the grayness.

Though sick and dizzy with shock, Mark found that he could move without pain. No bones broken then, he thought gratefully. By a great effort of will, he managed not to think about the terrible situation he was in. He had to keep cool, he knew that. If he gave up to fear and hysteria, he was lost and nothing could save him. He determined to conduct himself in such a way that his uncle would be proud of him.

His uncle. Would he ever see him again?

Mark pushed the thought away and struggled to his feet. He closed his eyes a moment, waiting for the dizziness to pass. He had no watch, and no way of telling how long he had been unconscious or what time it was. He smiled without humor. That, he realized, was a question that would take some tall answering. What time was it? Not in terms of minutes or hours, or the time of day. But what year, what century, what era? What time was it?

He opened his eyes. The red eye in the control panel looked at him, mocking him. Mark took a deep breath and examined the time dial. He started, unable to believe his own eyes. He looked again.

Mark heard laughter in the sphere, and he looked around sharply to see where it was coming from. There was nothing there. The machine was empty and he was alone. The laughter was his own.

He clamped an iron vise on his mind. The laughter stopped. He had to keep himself under control, no matter what happened. If his mind once snapped . . .

But it wasn't easy. The time dial that his uncle had spun was no longer set for 46 b.c. Nor was it set for 460 b.c. Nor was it even set for 4,600 b.c. . . .

The time dial now was set for the year 50,000 b.c.!

Mark shuddered. He was going back in time fifty thousand years before the birth of Christ—and there was nothing that he could do about it. He sensed the time stream flowing by him as the gray sphere carried him back, back across the centuries and the tens of centuries. He knew roughly where he was going, all right—that was the trouble.

Still somewhat dizzy, Mark sat down again on the floor to take stock of the situation. He forced himself to examine his problem rationally, as Doctor Nye had trained him to do. Frantic emotion certainly had a place—too large a place, perhaps, in human existence, but its place was emphatically not in the solving of problems. Mark knew that he had a brain, but that was not enough. He had to use that brain.

Mark thrust the humming of the space-time machine from his mind. He ignored the gray eeriness that surrounded him. He did not look again at the red eye in the control panel. As calmly as possible, he thought the problem through.

The space-time machine was carrying him back through time and space. In space, of course, he would no longer have Italy for his destination. As he understood it, however, the extra thousands of years would throw him off his course not too far toward the northwest—probably into what in modern times was known as France and Germany. In time, the problem was more difficult. Mark thanked his lucky star that his uncle had drilled him so thoroughly in history and prehistory. The year 50,000 b.c., he knew, would place him in the Pleistocene, or Ice Age. Further, it would place him in the last, or most recent part of it, known as the Upper Pleistocene. Beyond that, a peculiar problem presented itself. Authorities disagreed violently on the exact time sequence of this last part of the Ice Age, and the year 50,000 b.c. might fall almost anywhere, according to which system you followed. However, his uncle had believed that the year 50,000 b.c. would fall roughly in the Upper Paleolithic, or toward the end of the Last Ice Age—and that was as good a guess as any. He would just have to wait and see.

Mark looked carefully around the inside of the space-time machine, hoping against hope for some sort of miraculous aid. But there was no miracle. Everything was just as it had been when his uncle had left him—how long ago?—to answer the telephone. There were no supplies of any sort in the machine—no food and no water. And he knew that he would have to spend at the very least two weeks in the Ice Age before he could hope to return, in order to give the energy potential time to rebuild itself. That meant that, somehow, he would have to go out after food and water.

Knowledge can be a frightening thing, but it can also prevent you from worrying about nonexistent dangers. Mark knew that he needed to waste no time worrying about dinosaurs or other reptilian monsters, since they had died out millions of years before the first men were born. And there were men in the Last Ice Age—strange men . . .

Mark got to his feet and examined himself. He was dressed in blue jeans, which would be strong and able to take rough wear, and a long-sleeved wool shirt that would at least help to keep him warm. His shoes were less promising, moccasin-type loafers that would probably prove useless in ice or snow. He emptied his pockets as a check and found the usual things—a handkerchief, a comb, a pocket knife, a small box of matches that he carried in order to light his uncle's pipe when Doctor Nye forgot his own matches, which was most of the time, and a billfold containing ten dollars in bills and a few coins. He smiled—the money wouldn't come in too handy where he was going.

There was, however, one fortunate circumstance; Doctor Nye's .45 was still hanging in its holster from the side of the sphere. Mark took the gun down and looked it over. It was loaded, as always, with a clip of six cartridges. There was no bullet in the chamber, for safety's sake. Six shots, hardly enough for what he might have to face, but they would have to do. Mark buckled on the holster and felt a little better.

Then he sat down again to wait—there was nothing else to do. He had no way of knowing how much time had passed inside the sphere, nor did he know how long the journey would take. He was hungry, since he had missed supper, but that was no index. He was always hungry.

He tried to sleep, but it was impossible. He was more wide-awake than he had ever been in his life. But he closed his eyes and attempted to get what rest he could. What were his chances, really? He didn't know. But he did know that he was not going to give up. He would try, give it the best he had in him, and that was all anyone could do. And he knew, too, that he was fortunate in being as well educated as he was. He was not going into the Ice Age unequipped, and he suspected that what he carried in his head would in the long run prove more valuable to him than the .45 he carried in his holster.

Mark's first awareness that the space-time machine had stopped came when he suddenly noticed a complete absence of sound. It was dead quiet in the lead sphere. He opened his eyes. The gray atmosphere was gone and the air seemed stale and flat. The red light in the control panel was off and the yellow light had replaced it.

Slowly, Mark got to his feet. He hesitated a moment and then walked steadily toward the circular entry port in the side of the sphere.

near-by shrub, but did not recognize them and could not tell whether or not they were edible.

Far to the north, he saw a glint of what looked like an ice sheet, although it was too far away for him to be certain. It might have been some sort of mica-like mineral, or even a trick of the light from the setting sun. To the east, the grassy plains extended for miles, to be broken finally by a low range of snow-capped mountains some twenty or thirty miles away. The mountain range curved around toward the south, becoming somewhat higher, and Mark could see what appeared to be scrub pine trees in the near foothills that seemed to be no more than five or ten miles away from him. A low mist, clearly a product of the approaching coldness of the night, hugged the ground in tiny whorls and rivulets.

Mark hesitated, uncertain of what course to follow. He was stunned and dizzy from the shock of what had happened, and he was ravenous. He squinted at the sun and judged that he had still an hour or two of daylight left to him. But he could not be positive; he knew it would depend on precisely where he was and what time of the year it happened to be. Night could descend with fearful speed in some parts of the world, as he had seen for himself many times.

He thought it over carefully and then threw the switch that would close the entry port into the space-time machine. The circular door hissed shut. It wouldn't do, obviously, for some strange creature to wander into the machine while he was gone. Mark looked around, looking for he knew not what. Which way to go?

There was evidently game around in profusion, although he didn't care to tackle anything as big as the woolly rhinoccros-like animal he had seen, with only a pistol. He eyed the berries, but decided against them. It wouldn't help any to poison himself, and as a rule of thumb he knew that it was usually wisest not to eat anything you weren't familiar with. He had only one testing animal available—himself. And if the test turned out for the worst, he wouldn't benefit from the knowledge.

Mark decided finally to move due east, so that the sun's position could guide him back to the space-time machine. He hefted the .45 thoughtfully. It was heavy, but having it in his hand might mean the difference between life and death. He smiled and patted the dull lead of the space-time machine.

"Take care of yourself," he breathed fervently. "If anything happens to you, my name is mud."

He set out then, resolutely. The evening wind was blowing toward him, into his face, which was good— the animals wouldn't get wind of him and disappear. It was cold, and getting colder, but it was not unbearable and Mark's mind was on other things. He turned and looked back at the machine that had carried him across the ages. The great sphere squatted there on the plain, a stranger, utterly out of place under the deep blue sky with the little rivers of white mist beginning to curl around it as though curious about the odd thing that had suddenly appeared out of nowhere.

Mark kept going, on into the strange new world. He realized that it was funny he should think of it that way. This world was old, lost in the past byways of an almost forgotten history. And yet it was new too—new and fresh and clean with the scent of millions of wild flowers. Some of Mark's natural fear left him. If only he could find some food, it might not be so bad . . .

It was quiet save for the sighing of the grasses. Mark had never heard such silence before. Always, in his own time, there had been the mechanical noises of civilization all around him. The great cities clattered and banged in their dirt and grime, and in the green countryside the cars and tractors hummed and chugged. No matter where you went, the buzz of civilization went with you. Even far out on a mountain stream, alone, you would be startled by the thunder of airplanes or the whistling scream of jets. The silence now was uncanny—and somehow it seemed choked with life, invisible life that hid itself from his eyes.

Mark walked on, feeling his way, every sense alert. He had himself under control, and steadfastly refused to think of the terrors and the horrors which might confront him at any moment. He concentrated on the objective at hand, and did not think about the dangers and the coming cold and the loneliness. What he could not change could not be helped.

On he went, through the grasses and the flowers, with the red sun fading into dull orange and sinking lower and lower in the west. Soon, he knew, he would have to start back or else run the risk of getting caught out at night away from the space-time machine, his only refuge—a prospect that was far from pleasant. But hunger urged him on.

Mark began to grow uneasy as the long shadows walked along beside him and the cold breeze strengthened into a forcible wind. He hesitated and was almost ready to give up and spend the night hungry when he spotted movement ahead. Mark instantly dropped to one knee. Holding his breath, he peered ahead through the grass.

There was still enough light to see by, and he could make out dark patches not far away. They moved slightly as he watched, evidently grazing. Mark wormed his way forward through the grass, scratching himself slightly on small shrubs but not noticing the pain. He crept closer and closer, stalking the black shadows. They were just ahead of him now. Holding his breath again so that he made no sound, he carefully parted the grass and looked out.

There they were, five of them. Mark examined them intently. They were fairly large animals with shaggy manes. They had short legs and two small horns. They had a distinct hump on their front shoulders and they were heavy and bulky. For a moment, Mark was haunted by a distinct sense of familiarity. Where had he seen animals like these before? Then he had it. They were bison, buffalo, much like those which had once roamed the plains of America before their virtual extermination by white hunters like Buffalo Bill. There were four adults and one smaller calf, and they obviously suspected nothing.

Cautiously, Mark inched his way closer. He could not afford to waste one of his precious shots, and a .45, for all its smashing power, was a very erratic weapon as a target pistol. He settled on the calf as his best bet. It grazed a little apart from the others and should be easier to bring down.

Mark halted, a scant thirty yards from his prey. He checked his gun and slipped the safety off. He lay down full length in the grass and raised his pistol to take aim.

He never had a chance to fire. With a sudden snort, the lead bison lifted its head and broke into a lumbering run that covered ground with a deceptive speed. The others followed him instantly. Mark still had a shot of sorts, but he passed it up. He simply could not take a chance on missing, with bullets in such short supply. It had to be a sure shot or nothing.

There was something else, something that sent a cold chill through Mark that was not entirely due to the chillness of the coming night. Something had frightened the bison, and he was positive that it hadn't been himself. He lay very still in the grass, listening. He heard nothing. There was only the whisper of the wind.

It was growing late. With an alarming rapidity, the sun was gone and the long shadows of twilight were merging into the black of night. It was colder now, a wind-driven cold that threatened to drop the temperature far too low for comfort. Mark was painfully hungry. He had been so close to food that he could almost taste buffalo steaks in his mouth. And the skin could have kept him warm, if he could have managed to get it off with his pocket knife.

Mark did not want to move. He felt the weird presence of something alien in the shadows of the onrush-ing night. He felt unseen eyes upon him, boring into his back, lifting the hair on his neck. But he had no choice. He told himself that it was all imagination and got to his feet, the .45 ready in his hand. He saw nothing, but the shadows were thick around him now.

Desperately, he started back the way he had come, guiding himself by the faint lingering light behind the mountains in the west. He was grimly afraid that he

did not want to see them, not in the light. They were terrible enough dimly glimpsed in the darkness. The things walked on two legs, which were bent slightly, giving them a stooping posture. They were short, about five-feet-five. They had two arms, and they seemed to be carrying weapons of some sort. They were not apes—and yet they were not men either. They were half-men, and Mark knew that if he ever got a good look at them he might well go out of his mind.

One of them snarled hideously. The thing came forward. It touched him. Mark tensed. A foul animal smell assailed his nostrils. He dug the muzzle of the .45 into the thing's belly but he did not dare fire. He waited. If he was attacked, he determined to sell his life as dearly as possible. Otherwise—what?

The thing snarled at him again and jerked his arm.

"Who are you?" Mark heard a voice gasp. It was his own. "What do you want?"

There was no answer, of course. The things could not possibly understand what he said, even if they had a language of their own. But Mark had to talk. He felt better talking.

"What do you want? Get away from me, get . . ."

The thing snarled again and then screamed hideously. Mark shuddered. The half-men's eyes seemed to glow redly in the darkness, like monsters, like fiends from Hades . . .

The thing jerked at his arm again, harder this time. Its hand was rough and as hard as iron. The half-man growled deep in his throat. Again he pulled at Mark's arm, while Mark kept the .45 buried in the thing's stomach, his finger curled around the trigger.

Mark understood dimly what the creature wanted.

It wanted Mark to come with them somewhere, that was clear. Mark weighed the possibilities. He could shoot the thing arid make a break for it, but where could he go? It was too dark to see now, although the stars were coming out, and he could not find his way back to the space-time machine without a stroke of extraordinary luck. And the others would be all over him in a minute, ripping him apart, tearing at him. He had no chance and he knew it.

"Okay," Mark whispered. "Let's go."

The thing understood nothing of the words, but it seemed to sense the meaning of Mark's voice. The iron hand relaxed and Mark was free. The shadows of the half-men closed in around him and began to walk across the plain into the night. With a sinking heart, Mark kept in the center of them. Whenever he fell back or hesitated, a warning snarl kept him in line.

Mark kept the .45 ready in his hand. However, he had abandoned all hope of using it. It was very cold now, although the wind had died down with the coming of the night. It was very still, except for the shuffling of feet and the harsh sounds of breathing. From far, far away, as though from another world, he heard an awesome trumpeting like the cry of an elephant.

Mark shivered. If only he had a fire to keep him warm! He was not used to such cold, nor was he dressed properly to endure it, the chill going through his shirt as if it didn't exist. A fire. That gave him an idea. He still had the matches in his pocket—could he do anything with them? Mark had read stories in which people had startled savages by unexpectedly striking a match, and thus making good their escape. It was a slim hope, but worth a try.

Mark holstered his .45 and fumbled with numbed hands for his box of matches. He opened it and took out a match. With a fervent mental prayer he suddenly struck a light and held it aloft.

Nothing happened. The things looked at the light without even curiosity, their faces swimming in the feeble, flickering light.

Mark blew out the match, quickly. He wasn't going to get out of this by any such simple trick, he realized. And the sight of their faces, even half-seen by match-light, was almost more than he could stand. They were awful. Like men, and yet terribly, horribly different.

Mark walked on in the midst of the half-men, a grim suspicion growing in his mind. As nearly as he could tell by the stars, they were moving southwest. Toward the snow-capped mountains Mark had noticed earlier, and away from the space-time machine. Would he ever see it again?

Onward they went, with Mark's legs beginning to ache with weariness. His hunger was an empty knot inside him, and the cold numbed his body. He was very tired and his eyes burned with the dry flames of exhaustion.

The moon began to swing up on its arc through the night. It was a half-moon, a silver crescent, and its pale rays swept down on the shadowed world, lighting the things that walked beside him. Mark did not trust himself to look.

It was a nightmare procession, touched with the fantasy of the forever unreal. Under a frozen moon, across the plains of the vanished past of earth, Mark stumbled forward. And around him, unbelievable monsters from the fears and the legends of forgotten history, the half-men shambled over the mist-kissed grass, their red eyes gleaming in the black shadows of the night.

How long they traveled through the darkness under the moon Mark did not know. It seemed to go on forever, the shuffling of the feet and the harsh breathing all around him. Finally, he noticed that they appeared to have left the level plain. The ground was rising under him and his feet occasionally stumbled on sharp rocks. The grass had played out now and he could see the black outlines of scrub pines along the trail. The rise in the land became steeper and turned into low hills. Up they climbed, and Mark found himself gasping shallowly for breath in the cold, thinning air. Sharp pains lanced through his chest, and he knew that he was close to collapse.

The half-men set a murderous pace through the night. They seemed never to tire. The world became a horror of stooped figures and a merciless moon swimming through the stars. Mark was dimly aware of splashing through a rapid, icy stream, with the moon shimmering the rushing water with silver. Then they went on, with Mark's open shoes wet and cold and beginning to freeze.

Mark's mind blanked out. He kept walking somehow, but he was not conscious of it. His body went on functioning, his legs kept moving, but his body seemed to be something utterly apart from him. He was somewhere else, numb, floating through colorless emptiness.

The hills widened into a valley and then into a mountain pass. The hushed light of false dawn was just lighting up the world and Mark sensed, rather than saw, snow-capped mountains all around him. The half-men that he refused to see led him up a tortuous, rocky trail from the valley and then suddenly it was dark again.

Mark realized dimly that they were in a cave. Ahead of them, orange light danced and flickered on the damp walls. Fires. Sensing warmth, Mark's body moved forward more rapidly. The shadows played grotesque nightmare games on the cold cave walls.

Growls and mutterings greeted their appearance and Mark found himself in the light. A faraway corner of his mind was grateful that his shocked senses could not properly respond, that he could not see clearly. As it was, he saw—too much.

The things were terrible enough in the shadows of the night. Here, around the fires, they were monstrous. They did not look like apes at all—that wouldn't have been so bad. Apes were amusing, comical, in their happy imitation of men. There was nothing comical about these things, and the worst part of it was that they were clearly and unmistakably men.

Their legs were bent at the thighs and at the knees, giving them a perpetual stooping posture, almost like a gorilla. They had broad, massive shoulders and barrel chests. They had huge bones, heavily muscled, and their lower legs and forearms were short and powerful. From their bull-like necks, their great heads hung forward horribly. Deep-set, beady eyes peered out from under heavy eyebrow ridges and a large, projecting mouth faded back into a receding chin. They were bearded, and dirty hair grew down over their low foreheads. They were dressed in crude skins, and their hair showed around them almost like an animal pelt.

The cave was dirty. Old bones and decaying flesh littered the floor, and the smell was overpowering. Insects hovered around the creatures, like fleas around a dog. From time to time, the half-men made spasmodic attempts to brush the flies away, their brute mouths hanging open, revealing sharp white teeth.

The human brain and nervous system is equipped with many defense mechanisms. When shock becomes too great, when fear becomes too intense, something happens and nothing seems to matter any more. Mark had reached that state, and more. In the midst of horror, he had but one thought—get to the fire. His body was cold, numb, and the warmth from the blaze was like a breath of life.

Mark staggered forward, and fell toward the fire. But one of the half-men caught him and jerked him back. The things grunted at each other and Mark felt himself seized and shoved up a narrow trail inside the cave. He was thrown into a dank, wet cavern and collapsed on the rocks. Faintly, he was aware of the half-men shoving a great boulder across the small cavern entrance, cutting off the light.

Mark was sealed in. Cold and hungry, he gasped for breath on the wet floor of the cavern. He knew with cold certainty what had happened to him. Those half-men were unmistakable.

He was in the hands of the Neanderthals.

That was all. Mark could stand no more. A white pain lanced along his nerves, up through his chest, and exploded with a cloudy puff in his brain. With a hopeless gasp, he lost consciousness.

even after a rifle bullet through the chest? He smiled ruefully. It was different when you were real.

Mark moved silently through the gloom to the mouth of the sealed cavern. The big boulder did not fit flush with the sides of the cave opening, and he could see through the cracks. He looked out into the big cave of the Neanderthals and examined the entrance to their cavern. The light outside was gray, and he judged that it must be getting on toward evening. He had slept some twelve hours, then.

What could he do? He tried to move the boulder, but it did not budge. He did not waste his remaining strength, but stretched out again on the floor of the cave. There was a little moisture oozing out of the dank rocks, and Mark licked at it with his tongue to relieve the parched dryness in his mouth. Then he glued his eyes to the crack in the rock and determined to learn what he could, in the hope that some method of escape would present itself to him. He told himself that he was certainly smarter than his captors, and he still had his .45, and thus he bolstered his courage.

Mark counted twenty Neanderthals in the cave, many of them women and children. They were grouped around a central fire. At first, they seemed to be simply a pack of savages, moving around without aim or purpose. But as Mark watched he began to detect certain patterns that brought some semblance of order out of the seeming chaos.

The Neanderthals were still hideously ugly, even startlingly so, but they were somehow less revolting to Mark than they had been the night before. Perhaps it was because he was more used to them now, or possibly it was due to the fact that he had had some sleep and his jangled nerves were more settled. Probably though, Mark reasoned, it was due to their actions. For all their grotesque appearance, they were doing things that were unmistakably human.

Several of the Neanderthal women were engaged in building up the fire, taking dead branches, ferns, and moss from a pile in one corner of the cave and piling it on the crackling blaze. The little children, for all their ghastly looks, were almost comic as they tottered around after their elders, trying to drag branches to the fire. Mark spotted another woman scraping the flesh from a bison hide with a sharp stone scraper. The scraper was very crude and seemed to be too large for its purpose, but it was getting the job done.

There were no animals of any sort around. At the mouth of the cave, a Neanderthal man, who might have been a lookout, squatted on his haunches, flaking a chunk of rock with a hammerstone. By his side lay a short wooden spear tipped with a stone spearhead.

There were some animal skins scattered about, evidently for sleeping purposes. Behind the fire, there was a curious arrangement of bones and stones that could hardly have been accidental. Mark judged that the pattern had some sort of ceremonial significance. He noticed, too, that the bones were placed in distinct groups of four. Evidently the symbolism of a lucky number had made an early appearance in human society.

As Mark watched, there was a call from the man at the mouth of the cave and shortly five more men came in. They were burdened down with the carcasses of several small bison, and one of them carried a pile of roots and berries. All the men were armed with spears, and Mark was relieved to see that they had no bows. They dumped the meat in front of the women and snarled at each other. Mark could not catch any distinct words, but the half-men obviously had a language. From their gestures, Mark judged that they were arguing about the division of the meat. One of the men became angry and grabbed at a bison leg for himself, but two others instantly shoved him roughly away. Except for three men, the Neanderthals then split into several family groups and retired to separate parts of the cave.

The three men grunted at each other and one of them pointed toward the cavern in which Mark was imprisoned. They started toward him. Mark drew his .45 and waited. The time was not yet right to make a break for it, but it might be that he would have no choice.

As the Neanderthals approached, Mark's fear returned. Human or not, the half-men were not a pleasant sight. Mark stared at their sharp teeth and.won-dered. . . .

The three Neanderthals moved the boulder away from the cavern entrance. Mark got to his feet and faced them, the gun ready in his hand. He could smell them. What did they want? If only he could communicate with them, talk to them! Mark understood full well now what his uncle had meant when he warned against trying to go into a time stratum unprepared. If he could talk to them, he might at least have a chance.

One of the Neanderthals kept pointing at him and jabbering, and Mark finally got the idea that he was showing him to the other two. Mark was a prize exhibition. But he could see that the Neanderthals did not seem to be surprised at what they saw; they accepted him as a perfectly normal part of their surroundings. One of them poked at his clothes with what appeared to be curiosity, and another eyed his short-cut hair, but that was all.

Mark waited, the germ of an idea growing in his brain. It might be significant that the Neanderthals accepted him as an everyday part of their lives. Of course, it was always possible that they were simply too dim-witted to notice any difference between himself and the animals they saw all the time, but that was not probable. These Neanderthals, Mark knew, were in all likelihood much smarter than they looked. No, there must be some other explanation for their calm behavior. And Mark could think of only one possible answer. The Neanderthals must have seen men like him before. But where? How? Mark thought he knew . . .

After a time, the three half-men left him, resealing the mouth of the cavern with the boulder. Mark hol-stered his .45 and lay down again on the cold rocks. His hunger began to assert itself again, and he licked some more water from the side of the cave. What next? If something did not happen soon, it would be too late to do anything. He was growing weaker by the minute, and the rawness in his throat was getting worse in the damp air of the cave. He looked outside and judged that night had come once more.

The flickering fires threw long crawling shadows on the cave walls, and the half-men moved through the dancing light like creatures from a long-forgotten dream. Mark watched them roast chunks of meat on long sticks and then gorge themselves with food. His hunger became almost unbearable as the smell of roasting meat drifted up into his tiny cavern.

After the Neanderthals had eaten, Mark witnessed a strange sight. Methodically, as from long habit, the half-men shuffled into position behind the fire. There, fitting themselves into places between the ceremonial rocks and bones, they stood silently for a moment. One of their number, a man with a band of red painted across his low forehead, screamed loudly four times. Then he fell to his knees and four times he pounded his head against a large skull that looked as if it had come from a mammoth.

There was silence. The long shadows played among the stooped figures. Outside, the cold wind moaned across the cave mouth like the cry of an impossible spirit, forever dead, forever longing to be born.

Mark watched, fascinated despite the seriousness of his position. At what must have been a prearranged signal that he had failed to catch, every Neanderthal except the man with the red band on his forehead picked up a long white bone and started to beat it on the rocks. A rhythmic clicking filled the cave. Once more, the number four was predominant. The rhythm was a distinct pattern of a series of fours followed by short, sharp silences.

It was a scene to stagger the imagination, and its effect was not lost on Mark. Here in the dawn of time the first groping men stood in the black shadows beyond the leaping flames and made their rude music out of bones and rocks. There was something infinitely sad about the creatures in the cave, something that was past all knowledge or expression. Almost, Mark could pity them, horrible as they were. They were not really human—and yet they were not wholly animals either. There they lived and dreamed strange dreams, and all the while the great Wheel of Time rolled mercilessly on, wiping them out even as it wiped out the vast ice sheets that had been their home. The Wheel turned, grinding them under . . . But they were not gone yet.

Suddenly, the clicking stopped. The hush was deafening. The Neanderthals stood without moving. There wasn't a sound in the cave except the sputter and hiss of the fire. Three men detached themselves from the group, the half-man with the red band across his forehead in the lead. They came across the cave floor, straight toward Mark.

Mark smiled coldly. The ceremony had been for his benefit, then. He was to be the star performer. He could not know exactly what his part would be, but he could guess. It wasn't that the Neanderthals hated him in particular, or in any way regarded him as unusual. This was evidently just the process they went through whenever they got hold of anyone like him. What was the Army phrase he had heard his uncle use?

Standard operating procedure.

What would happen to him? Obviously, a group like the Neanderthals, living as they did on a bare economy of essentials, would have no use for prisoners. A slave was of little use in such a society, being more trouble than he was worth. Mark had not been fed, nor had he been given anything to drink. It was clear that they were not going to leave him alive. His death might be fast or slow, but death it would be. Were the Neanderthals cannibals? Possibly—but Mark was not worried about what would happen to him after he died. He wanted to live.

There would be no more waiting, no more hoping for a better chance. This, he knew, was it.

The three Neanderthals thrust aside the boulder at the cave mouth. The half-man with the red band on his forehead growled at Mark and Mark understood that he was to get up. He thought carefully and drew the .45; arid this time he knew that he would use it. But he did not fire yet. He pulled himself to his feet and then swayed dizzily. He shook his head at the half-man and stumbled. He tried desperately to get across the idea that he was too weak to walk.

The half-man snarled again and grabbed his arm. His grip was like jagged steel and his long, dirty nails dug painfully into Mark's flesh. Instantly, he shifted the .45 to his other hand. If they tried to take it away from him, he would have to break for it at once, and that would take at least three precious shots . . .

But if the Neanderthals noticed the gun at all, they paid no attention to it. Mark's trick—it wasn't much of a trick, since he really was weak—worked and they evidently considered him too helpless to worry about. Two of the Neanderthals moved on ahead, going back to the ceremony beyond the fire, leaving Mark with the painted half-man.

Mark waited until they were clear of the little cavern entrance. The path to the outside world was open. It was dark and cold outside, but that did not matter. It was now or never.

Mark hesitated only a moment. The half-man was a horrible travesty of a man, but for all of that he was a man. Mark had never killed a man, and even now . . .

But he had no choice. Tensing himself, Mark suddenly came to life. He stopped short, and the surprised

Neanderthal stopped with him, although the steel grip on his arm did not slacken. The half-man growled low in his throat. Mark looked him in the eye. He raised the .45 and his hand was steady. The half-man, not even knowing that it was a weapon, looked faintly puzzled.

Mark aimed right between the eyes and squeezed the trigger. There was a blasting roar that seemed to shake the cave, echoing and re-echoing back into the dark depths. The gun kicked back in his hand, and the grip on his arm fell away as the surprised Neanderthal, still with a puzzled look on his face, crumpled to the cave floor.

Calling upon hidden resources that he hadn't known he possessed, Mark dashed for the cave entrance. The rocks stabbed at his feet and he had a wild, irrational fear that he would lose his wet shoes. His heart pounded wildly in his chest and he clenched his fists, clutching at the smoking .45. Which way could he go? How long could he last?

In desperation, Mark increased his speed, racing like a scared rabbit out into the darkness of the cold night. He remembered all too well the terrible stamina and speed of the half-men. He ran frantically down the rocky trail and into the starlit valley he had stumbled through—when? It seemed like a million years ago.

Mark felt his exhausted body crying out in protest. He was weak with hunger and fatigue, and he knew that he could not hold out for long. Gasping for breath, he heard behind him the shouting snarls of the maddened Neanderthals.

running south. South, but veering a little to the east, just enough to miss the half-men, if he was lucky. If he wasn't lucky—

They wouldn't be expecting him to double back, of that he felt sure. He drew his .45 and ran bent over almost double, only a shadow among the shadows. He was close to them, he was even with them, he could smell them in the night—

With horrifying suddenness, a figure loomed up right at his side. Mark dropped like a shot and wriggled through the wet grass on his stomach. Had he been seen? He fought to control his breathing, but it was impossible. Had he been seen? Evidently not. There was no alarm. His body one aching agony, Mark lurched to his feet and ran on.

He wouldn't fool them long, he figured. They would be back after him. But he knew now that he did not have so much as a prayer on the open plains in the moonlight. The Neanderthals were stronger than he was, and there were more of them. Even as he ran, a small subconscious corner of his mind wrestled with the problem. It was the old, old game of man against man, the hunter and the hunted. But one factor at least was changed—now it was man against half-men, and that made a difference. It had to make a difference. It was his only hope.

Mark angled along the slope of the foothills, bearing somewhat east from the valley of the Neanderthals. The sounds of pursuit were almost lost in the distance now, but Mark did not fool himself into thinking that he had given them the slip. They would pick up his trail and come on, snarling, untiring, like mighty hounds on the scent of a desperate fox. He was the fox.

The foothills continued for a long time, with the dark mountains that shielded the Neanderthal caverns fading by on his right. The ascent was becoming steeper, however, and the scrub pines that dotted the foothills were getting fewer and fewer. Mark redoubled his efforts, but his best speed now was no more than a jagged trot. If he could just reach the mountains, hide himself somehow, somewhere . . .

But the Neanderthals would surely know the mountains around their home well enough to search him out. Mark gasped for breath. He had no hope now, and he knew that he was fast reaching the ultimate limits of his reserve strength. He could only go until he dropped, and then there was the .45. Five shots left. Four for the half-men— And one for himself.

Mark hurled himself into the mountains. The rocks tore at his beaten body, but he kept going. Up and up, and always bearing toward the east, away from the valley of the Neanderthals. He scrambled up smooth cliffs and plunged through snowdrifts, white and ghostly under the stars. He had no way of knowing whether the drifts were a few inches deep, or a few feet, or a few miles, and he had no time for caution. Certain death was behind him, and chance, no matter how slim, was better than that black certainty that pursued him.

His luck held, and he stopped going up the mountain and struck off due east across the snow. He knew that he was leaving footprints, but that couldn't be helped. Or could it? Ahead of him he saw a black crevice, a deep pass in the mountains. Seeing it clearly before him, dark beside the whiteness of the snow, was the first indication that he had that the moon had risen. He looked up. There it was, coldly beautiful as ever, a silver crescent hanging from the frosty stars....

A wild thought raced through his mind. In his own time, they were preparing to launch a rocket for the moon. Could it be? Did that future time, his time, really exist somewhere? Or was it all just part of the nightmare? Which was the real world, now—or then?

Mark shook his head. He had to hurry. From far below him, he heard the cold chuckle and gurgle of running water. He smiled, beyond pain now, beyond anything save the will to try. He was stripped down to bare essentials now, down to the will to live.

What was the phrase? Survival of the fittest. Well, he would see.

Gingerly, Mark lowered himself over the brink of the chasm. He could see the outlines of rocks and ledges in the side of the pass, and he would just have to trust to fate that they would support him. Going on raw courage alone, Mark fought his way down into the mountain valley. It was hard going, impossible going, and far below him he saw the silver shimmer of the stream, like a cold snake writhing forever across the frozen earth.

He made it, although afterward he never remembered how. He came back momentarily to his senses and found himself standing on the bank of the rushing stream, with the dark shadows of the mountains all around him. He heard nothing but the rustle of the water, but he took no chances. It would be folly to stop now, with victory almost in his grasp.

If he could just hold out—

Which way to go? Mark debated a moment, and decided that his pursuers would expect him to go upstream, into the mountains, away from the plains that had almost trapped him. So Mark went downstream. He stepped into the icy water without even feeling it and fumbled his way across the slippery stream bed. If there were any holes ahead of him, invisible in the moonlight, it would be too bad. But as long as he stayed in the stream they could not follow his trail. Mark's exhausted mind gave out, but his body kept on.

While the moon sailed serenely through the night sky and the stars marched through the heavens, Mark Nye splashed grimly onward through the icy water of the mountain stream. He struggled on for what seemed to be miles, until the stream ran bubbling out into the plains. Mark dragged himself out of the water and headed east again, away from the Neanderthal caverns and away from the space-time machine that he had little hope of ever seeing again.

The ground was wet and marshy around him, but Mark was unaware of it. He put one foot mechanically ahead of the other and plodded on, his shoes making sucking noises in the soft earth. His pace had slowed to a virtual crawl, and he knew that he had to find some place in which to rest.

He kept on until he could go no farther and then cut back into the mountain foothills. He looked around him dazedly. There were a few pines, but nothing that offered any hope of concealment. He was just on the verge of collapsing where he was and taking a chance when he noticed an outcropping of rock on a little ledge above him to the east. He crawled up to it, hand over hand, unable to stay on his feet. He pulled himself over the outcropping and found a slight depression in the rock wall, surrounded by large and formidable boulders. He dragged his body inside, where he was at least sheltered from the cold wind.

It was not the best possible place, but he could go no farther. He was wet and numb with cold, but he knew that he did not dare to build a fire, even if he had had the strength to do it, which he hadn't. He took out his .45 and wiped it as dry as he could on his torn shirt, and then returned it to its holster. Gasping for breath, his chest aflame with pain, he thought briefly of climbing out to get some snow he saw. He could eat the snow and thus quench his thirst a little—

But his body refused to move. It had served him well, but it was spent. Mark heard his heart beating with a rapid, exhausted flutter and he could not even move his hand.

He was hopelessly cut off from the space-time machine. He was ill and unutterably tired, without food or water. He did not even have the satisfaction of knowing that he had eluded the Neanderthals; they might be right behind him, and he was too weak even to pull the trigger of his .45. Mark looked at the cold moon, now fading in the east. From the plains that stretched below him, he heard the trumpeting cry of some animal that he could not even imagine. For the first time, he became aware of the enormity of the thing that had happened to him. He was only a boy, after all, and he was tired and hungry and terribly alone. A line from a poem he had once read whispered through his mind in the dawn of time . . .

I, a stranger and afraid—In a world I never made ...

Mark coughed brokenly as sleep washed over him like a warm and comforting sea. He was a long, long way, and a long, long time, from home.

Mark became aware of the fact that he was lying on his back, and he rolled over on his side. The rocks that had sheltered him were warm and friendly now, no longer the dark behemoths of terror that they had seemed the night before. The scrub pines stretched away down the foothills below him, and beyond them was the grassy plains. The scent of pines was strong in the air, and sweet. Mark saw that the sun was directly above him. It must be noon.

Cautiously, he tested his dry throat. It was still raw and sore, but it seemed little worse than it had been before. Mark knew that the sun had saved him for sure, the sun and the rocks. The great boulders had shielded him from the cutting wind, and the sun must have come up shortly after he had collapsed, warming him and drying out his wet clothes. Mark felt like a new man, through with the terrors of the night and ready to face life again with a fresh spirit.

Mark got to his feet, and his new strength promptly deserted him. He swayed dizzily and almost fell, but caught himself on one of the boulders. He stood with his eyes closed for a moment, waiting for the spinning in his mind to stop, and then struggled erect again. This time he made it, but he was fearfully weak.

He panted from the slight exertion and tasted the dryness of his throat. His mouth felt as if it was full of cotton, cotton that had the fiat, metallic taste of copper pennies. His thirst came back with a vengeance, and with it came a gnawing hunger.

He had to have food—and he had to have it in a hurry. Mark moved carefully from his retreat, every sense alert. He saw nothing that looked dangerous. There was only the blue sky, and the sun, and some faraway tiny shadows on the plains that must have been birds. He crawled up over the ledge, and walked slowly to where he saw a patch of snow under a large rock. He fell to his knees and scooped out a handful, which he forced himself to eat slowly. The snow melted deliciously in his mouth and trickled down his dry throat. Mark ate another handful, and another, and then he felt a little better—well enough, at any rate, to make it to another stream. Water was everywhere in the mountains, and he expected to have no trouble finding it.

Mark waved a weak farewell to the little shelter that had saved his life, and made his way back through the foothills to the edge of the marshy plain. He moved slowly, conserving his strength. He thought for only a moment before he set out once more into the east, determined to put distance between himself and the half-men. Of course, there might be others ahead of him—he had no way of knowing. But that was a chance he had to take.

Mark kept a wary eye out, but he saw no game. He tried not to think about how hungry he was, but he couldn't help it. He began to construct wondrous edible fantasies as he walked along. He could see himself sitting down at a table in his uncle's home—the little table in the kitchen, with the clean white tablecloth on it. And there was salad, and turkey soup, and a thick charcoal-broiled steak with hashed brown potatoes, and banana cream pie . . .

Mark smiled ruefully. It was going to be a long time before he saw banana cream pie again. Banana cream pie was fifty thousand years and more away . . .

He kept going, not daring yet to eat the red berries that grew in profusion all around him. He was desperately lonely. In many ways, his loneliness was the worst part of it. Mark had never before realized how completely dependent he had been on other people. In the modern world, in the world he had known, you were never truly alone. If there was something you needed, you went to someone else and got it. If you were hungry, you opened a can that had been processed in a factory. If you were sick and could not move, you picked up a telephone and help was at your side.

A telephone. If only his uncle had not gone upstairs to answer the telephone! So long ago—or was it yet to be? If only his uncle were with him now!

But he wasn't. Mark could turn to no one—he would have to make it alone or not at all. The sun felt good on his back, but the leather in his shoes had dried out and was now stiff and hard. His feet hurt. But it couldn't be helped. He kept going.

Finally, he noticed a small clump of shrubs ahead of him and hurried forward as best he could. His eyes had not played tricks on him; he knew the signs of water when he saw them. A small, still pool bubbled out of a spring before him. The water was fairly deep, but clean and pure. Mark could count the pebbles on the bottom. He flopped down beside the clear water and drank his fill. The water was delicious, and he was much refreshed. He got to his feet again, and instantly dropped to all fours and wriggled back into the shrubbery, tugging at his holstered .45.

His heart pounded joyfully. Here was his first real stroke of luck. Mark crossed his fingers and held his breath. If only this dream did not dissolve in smoke like all the others!

It didn't. As Mark watched, a stately stag walked daintily out of the brush on the far side of the pool and sniffed the air. Then, as though convinced that he was alone and at peace with the world, the stag lowered his muzzle and began to drink. Presently, he was followed by two does and a small fawn. They looked like common reindeer, or caribou, although they appeared to be slightly larger.

Too nervous even to breathe, Mark took careful aim at the buck. His hand trembled, and twice he lowered the gun to steady himself. One of the does sniffed nervously at the air, and the buck raised his antlered head inquiringly. Mark could hesitate no longer. He aimed the clumsy .45 and squeezed the trigger. There was a smashing report, unnaturally loud in the stillness, and the buck spun and leaped for the shrubbery behind him. Mark cried out despite himself.

He had missed!

Mark leaped to his feet and desperately fired again. In mid-air the buck faltered. He came down trying to run, but Mark spotted the telltale red wetness on his left shoulder. He took careful aim but held his fire. He could ill afford to use up another bullet, but he was prepared to do so if he had to. But it wasn't necessary. The buck managed a few staggering steps and then collapsed in the grass, his great sad eyes looking at Mark in a way that was almost human. The fawn nosed the fallen buck in confusion, then followed its mother away across the plains.

Mark came forward, his hands shaking with excitement. He knelt beside the reindeer and fumbled for his pocketknife.

"Sorry, old boy," he murmured, "but I never needed a meal in my life like I need this one."

Mark set to work, but it was tough going. The blade of his knife was razor-sharp, but it was not made for carving. He sawed around the right foreleg, cutting through the skin and as many tendons as he could. Then he placed one foot on the leg between the shoulder and the cut, and attempted to break the bone by force. In his weakened condition, it was far from easy. But he managed, and then carved out several good cuts with his knife.

There might be Neanderthals lurking near, but Mark reasoned that if his shots had not drawn their attention then, nothing else would. Hungry as he was, he did not intend to eat his meat raw. A flat rock by the pool would serve as a fireplace, and the shrubs should kindle up into a good enough fire. Mark found enough shrubs within twenty yards to more than satisfy his needs, and he hacked branches from them with his pocketknife. He trimmed them of foliage and then carefully split several of them down into sections. These he shaved into fine slivers for kindling. He arranged the wood with meticulous care on the flat rock, building it up from tiny shavings to fair-sized branches. He trimmed one stout branch to a sharp, twin-forked point and he was ready.

Mark fished out his matches and struck one on the box. It failed to light, and he saw that the matches were damp. He felt a sinking sensation in the pit of his stomach and began to realize what primitive man was up against. Suppose he had to make his own knife, where would he start? Suppose he had to kindle a fire from a chunk of wood and an improvised drill? Sure, it looked simple enough in the diagrams—but could he do it?

Mark wasted six matches before one hissed and caught. He cupped the priceless light in his hands and applied it to the wood shavings. The wood was damp from the night mists, the flame flickered very feebly and almost died. Mark realized he had never appreciated a fire before. Fires were always something you just took for granted, but not now. He concentrated every atom of his being upon that scanty blaze. He blew gently on it, but it would not catch. He frantically lit another match from the tiny flame and tried again with the same results. He knew that if he could once get a reasonably hot blaze going, however small, the fire would catch. But how? He needed paper, and there just wasn't any paper.

Or was there?

With sudden inspiration, Mark dug out his billfold from his pocket, all the while fighting to keep some sort of flickering flame alive. The billfold was damp, but not wet. He fumbled it open. It was dry on the inside. Hastily, he slipped out five dollar bills. He tore one to shreds and sprinkled them gently on the tiny spark. They hesitated and then caught with little puffs of flame. Mark built the other four bills around them like a tent, and slipped slivers of shaved wood in on top of them. He held his breath. The flame wavered—and then caught with a crackle.

Mark watched the little fire heat the wood and move on, spreading to the larger kindling and then to the branches themselves. He watched the fire as though he had never seen a fire before, as though it was the most beautiful sight in the world. He watched it in utter fascination, until the heat drove him back.

Mark slipped the matches into his billfold and returned the billfold to his pocket. Gratefully, he speared a reindeer steak with his twin-forked stick and held it just above the blue point of the crackling flames. The red meat contracted and juices fell hissing into the fire. The smell of roasting venison filled the air, and Mark sniffed it with complete pleasure. He had never been so hungry in his life, and nothing had ever smelled so good to him.

After the venison had been thoroughly cooked, Mark took the steak from the forked stick and placed it on a flat rock. He used the knife and a small stick to cut the meat up into thick sections, and then he ate. The venison had the zestful tang of game meat cooked over an open fire, and Mark would have declared without a moment's hesitation that it was by all odds the most delicious meal he had ever eaten. When he finished, he swallowed more cool water from the pool and put another steak on the coals to cook.

Comfortable at last, Mark lay back in the afternoon sun and just enjoyed feeling human again. Now that he had the chance, he determined to skin the reindeer before evening. He was not going to get caught out another night without protection of some sort. He knew nothing about curing hides, but he figured that if he scraped all the meat off and then dried it in the sun it would serve his purpose and keep him warm.

Then there was the meat. It had taken two shots to down the reindeer, and he had used one on the Neanderthal, which left him with three shots in his

.45. He could not afford to waste the meat, but on the other hand, he certainly could not eat it all before it spoiled. Mark decided to cut up the choice sections, wrap them in leaves, and bury them deep in the snow. That was as good a deepfreeze as he could ask for, and the meat cache should keep him alive for weeks if necessary.

Mark got up and speared the other steak, which he cut up as he had the first. He ate this one more slowly, savoring the fine flavor, and he actually found himself feeling uncomfortably full. Then he lay back again in the grass and permitted himself the luxury of relaxation. It was good just to be alive, and danger seemed a remote and unreal thing under the blue sky, with the white clouds drifting by, the smell of flowers and green grass in the air, and the warm afternoon sun beating gently down upon him. Good just to be alive! Mark realized sleepily that he had never truly appreciated that before. When you tottered on the brink of the Valley of the Shadow, and then came out once more into the sunshine, you looked at things with new and deep-seeing eyes.

Mark nodded, half-asleep. He rolled over on his stomach, yawning. He looked into the still waters of the pool—and suddenly stiffened. He knew instantly that he had been guilty of the greatest mistake of all-he had won through, only to let his guard down when victory was in his grasp. A dark shadow was reflected in the pool, silent, unmoving.

Someone, or something, stood behind him!

Neanderthal, but a man. He carried a bow at the ready, with a feathered arrow taut against the bowstring. He was tall, perhaps a shade under six feet, and he was a magnificent physical specimen. He was bronzed from the sun, but recognizably white. He was dressed neatly in furs, with his powerful arms and legs bare. His hair was long and black, but neatly arranged and tied with a rawhide thong. His face was broad and strong, and he reminded Mark of a tall Indian, though he lacked Mongoloid characteristics.

Mark looked at the man, and the man looked at Mark. Both seemed equally surprised, and uncertain of how to proceed. Neither dared to lower his guard, yet neither seemed ready to kill without cause. Mark realized that the man could have killed him at any time, and that he even now considered Mark unarmed. The man was evidently not a killer unless he was prompted, but one glance into his cold black eyes convinced Mark that death would be swift and sudden if he made a wrong move.

The scene held, a moment frozen in time. Mark did not want to shoot, but on the other hand he could not know when the stranger would take a notion to release that arrow. He waited. The man waited. The sun seemed to stop in the blue afternoon sky, watching. Mark noted that he was sweating, and not with heat.

"Orn?" said the man suddenly, his voice deep and steady. It sounded like a question.

Mark felt keenly the language barrier that stood between them. The man had asked him something, and waited for an answer. But what could he say?

"Friend," Mark said, feeling that it was best to say something, even if it could not be understood. He spoke slowly and as calmly as he could. "I am your friend."

The man looked at him, unmoving. His black eyes were unreadable. The arrow did not waver. Mark wondered at the strength that held that taut bow as steadily as a rock.

"Orn?" the man asked again.

Mark hesitated and then very slowly he got to his feet. The man stepped back instantly, and the bow tensed still more. Mark managed a smile. Should he shoot?

"I am your friend," he said again. Cautiously, so as not to alarm the man, he raised his left hand, palm outward, in a sign of peace. With his right, he held the .45 at the ready. The man watched with intelligent eyes, but it was at once obvious that the sign meant nothing to him. Mark lowered his hand and smiled again. The man did not move, nor did the bow relax in any way.

"Orn?" the man asked once more, his voice hard. This time it sounded like an ultimatum.

Mark's finger tensed on the trigger, but he could not forget that this man had spared his life when he might have killed him in cold blood. The man was an unknown factor. What was he like? Mark had to know before he could come to any understanding with him. If only he could make him understand that he was not an enemy!

With sudden inspiration, Mark moved very slowly over to the ashes of the fire. The man's eyes followed him, but he made no move. Mark reached over and picked up one of the reindeer steaks that he had cut but not cooked. He held it out to the man with his left hand, still holding the .45 in his right, ready for instant action. The man looked at the meat, and his grip on the bow relaxed just a trifle. Mark started toward him, holding out the meat. At once, the man backed away again and the bow tensed in his hands.

This was a crucial moment, and Mark knew it. The friendship or the hostility of this fur-clad man might very well mean the difference between life and death to him in this strange world. Mark hesitated and then placed the steak on a rock at his feet. He pointed to it, and he pointed to the man. Then he backed slowly away, leaving the meat unprotected.

The man watched him, his face still expressionless. A long minute passed. Neither moved. Finally, with sudden decision, the man relaxed his bow. He took the arrow and replaced it in a hide quiver on his shoulder. He stepped forward, still not taking his eyes off Mark, and picked up the meat. He smiled, showing fine white teeth.

Mark smiled back and holstered his gun. He realized that the man was not placing himself in Mark's power, at least not to his way of thinking. He still thought of Mark as unarmed, and his putting aside of his bow just meant that he had abandoned the idea of killing Mark, at least for the present. No doubt he figured that he could handle Mark with his bare hands if it came to that, and looking at the man's bronzed muscles Mark did not question his ability to do so.

The man evidently did not eat his meat raw. He walked over to the ashes of the fire and stirred them up. He threw some shrubs on, and kindled a new blaze from the still-hot coals of the old. Using the same stick Mark had used, and looking with interest at the sharpness of the points on the double fork, he roasted his steak. Permitting it to cool only slightly, he picked up the meat in his hands and gnawed at it with great satisfaction. Then he washed off his hands in the pool and sat down a short distance from Mark, looking at him curiously.

The strange man did not try to speak, clearly having proved to his own satisfaction that he could not make himself understood. It was probably no novelty to him, Mark thought, to run across a man like himself who did not speak his language. Doubtless his people were not organized into anything larger than extended family groups or bands, and each group might very well have a tongue of its own. It was possible, however, that there were a few words generally understood by several local groups, of which the term "orn" was no doubt one example. What did it mean?

Mark had received thorough linguistic training from his uncle, but his training was of little help to him in the present situation. A word might mean anything, of course. A word was not a thing. A word was a symbol that stood for whatever a group of people had agreed to have it stand for. A word like "orn" might stand for literally anything, and the only clue that Mark had to go on was its context, the situation in which it was used. At a rough guess, he figured that the word probably meant "friend" or something like that. Used as a question, it could carry the notion of asking whether Mark was hostile or peaceful, friend or enemy. Following that line of reasoning, Mark could see that if his guesses were correct, all he had to do was answer him with the same word, inflected as a

following this with more wood to act as weights against the wind.

They had a very serviceable lean-to now, and they kindled the fire up just in the entrance. Mark could see the rain coming in a vast gray sheet across the plains, and he hurried to gather some wood to keep the fire going during the night. Then he dived into the shelter with the dawn man, and not a moment too soon. The rain hit with a hiss and a roar, while the thunder crashed over their heads as though determined to rip the shelter to bits by the power of sound alone.

It was quite comfortable in the lean-to, and Mark looked at his companion and wondered how to go about making some progress toward understanding. He decided to try to learn the man's name as a first step.

In the firelight he pointed to himself. "Mark," he said, shouting to make himself heard above the smashing of the storm.

The man watched him intently, but made no sign. Mark's spirits fell. Had he perhaps overestimated the man's intelligence? What did he know about him really?

"Mark," he said, trying again. "Mark."

His companion nodded slowly. "Mark?" he asked, pointing. The word sounded very strange on his hps; it was recognizable, but seemed to have been somehow translated into another language.

Mark was delighted. "Mark," he said again, and then pointed at the man.

This time his companion got it at once. He pointed to himself. "Tlaxcan," he said slowly. "Tlaxcan." He smiled.

Mark smiled back. They could not go much farther with the storm raging around them, but they had made an important start. Mark listened to the rain and the thunder, and was thoroughly glad that he was under the lean-to. The slow hours whispered by, and Mark saw that the man had gone to sleep. Mark closed his eyes too, but sleep was slow in coming. The storm howled miserably in the night, and he could not forget that he was not two feet away from a savage who for all he knew might take a notion to knife him at any moment. Mark found it difficult to think of the man as a savage, but that, by definition, was what he was. Mark told himself that he trusted the silent figure who shared the shelter with him, but nevertheless he found that sleep was slow in coming.

Who was this man? Clearly, he was no Neanderthal, and was not even related to that weird and hideous race. Who were his people, where had he come from? Mark thought he knew, and the germ of a plan was beginning to plant itself in his mind. A plan that might one day get him back to the lead sphere of the space-time machine, cut off from him now as surely as if it had been whisked away to another world.

It was a long night. The storm whistled around the little lean-to, and the cold wind and the rain sighed up the mountain valleys. Twice, Mark crawled over and put fresh wood on the fire—and twice he saw TIaxcan's eyes open and watch him. The man evidently slept like a cat, and no more intended to put himself at Mark's mercy than Mark cared to put himself at TIaxcan's.

Mark thought of his uncle, there in the night and the howling storm. His uncle would be terribly, frantically worried, he knew. Mark was all he lived for, and if something happened to him, there was no telling what might happen to Doctor Nye. It was very difficult to shake off the notion that every minute, every hour, that passed was torture to his uncle, far away in time, but such was not the case. Hard as it was to understand, the fact was that time was not necessarily going by at the same rate of speed for both Mark and his uncle. That is, for every hour that passed here in the long-ago world of the Old Stone Age, another hour did not have to pass for Doctor Nye in 1953. Mark could see that a little ingenuity would save his uncle most of his suffering. For instance, if he could once get back to the space-time machine, he could set the controls for a time not more than fifteen minutes after his uncle had first dashed upstairs to answer the telephone. Thus, even if months or years passed here in the dawn of time, even if Mark lived his life and became an old man, only fifteen minutes would have passed in the life of Doctor Nye. It was hard to believe, but Mark knew that it was true.

As the black night wore on into morning, Mark grew drowsy and gradually relaxed. It was good not to be alone any more, and even though he could not talk to Tlaxcan he felt a genuine kinship with him. He looked across at his dark sleeping form, and the night seemed somehow less cold and fearful. How strange it was, he reflected, that they should have met. What were the odds on any two people meeting in the twisted destinies of the world? What were the odds on them, two who had lived their lives separated by a gulf of almost fifty-two thousand years?

Mark did not know the odds. There in the shadows

Mark saw a herd of animals in the distance, grazing on the plains, and at first he thought they were bison. But as he looked more closely he changed his mind. It was difficult to tell so far away, but the herd looked for all the world like wild horses, with several small colts frisking happily about in the sunshine. Mark tried to remember whether or not there had been horses in the year 50,000 b.c., and then he smiled. There the horses were, and after all was he not the world's greatest authority on this Ice Age? He was the only modern man who had actually been there.

Then Mark saw something else. To his left, over the spot where he had left the dead reindeer by the pool, a cloud of great black birds hovered on widespread wings, drifting in the breeze, landing, and gliding in endless circles. Mark shuddered. Vultures, the grim scavengers of the dead . . .

He became aware of still another cloud of the devil birds to his right, and it was a moment before the significance of the sight sunk in. Tlaxcan! The vultures would not venture near his kill if he was all right himself. Of course, he could have left a carcass behind him and started back for the shelter, but if that was the case, either he was moving very slowly or else the vultures had moved in with unusual speed. Something told Mark that there was no time to waste.

He grabbed up Tlaxcan's stone knife and drew his .45. Taking a careful sight on the cloud of vultures so as not to miss his directions, he scrambled down from the rock and left their camp on the double. He did not try to sprint, knowing that he had too far to go for that, but kept to a steady trot that covered the ground with rapid speed. He loped out of the foothills and onto the grassy plain, and then cut eastward to where he could still see an occasional vulture flying higher than his fellows.

It took him over half an hour, and at his approach the great ugly birds rose higher into the air, their gruesome naked necks arched in dismay. Carefully, Mark picked his way through the shrubs until he saw that his fears had been only too well warranted. Tlaxcan had propped himself up against the dead body of his prey, a very large wolflike animal that looked something like an overgrown Arctic fox. The wolf-thing was dead, but it had given a good account of itself. Tlaxcan had driven two arrows completely through the beast, but Tlaxcan himself had been clawed badly on his left shoulder. The blood had run down his side and dried in a dark mat, although it was still thickly red at the wound. Somehow, Tlaxcan had retained his senses and had actually been using his bow to good effect with his shoulder clawed and bitten fearfully, as one dead buzzard with an arrow through its neck mutely testified.

Tlaxcan had heard him coming, and Mark once again found himself with one of Tlaxcan's deadly arrows staring him in the face. But Tlaxcan recognized him at once and lowered his bow. He smiled feebly and tried to get up, but couldn't make it. His tense face was white beneath its tan, and Mark could see that he had lost a lot of blood.

Mark came forward and knelt beside the fallen man. He was still oppressed by the fact that he could not speak and make himself understood, but Tlaxcan solved this problem for him neatly. He put his right hand on Mark's shoulder and looked searchingly into his eyes, then lowered his hand and sank back. Mark understood—Tlaxcan was putting himself in Mark's hands. Facing almost certain death if he were abandoned on the plains, he was trusting a stranger to save him.

Mark examined the wound in Tlaxcan's shoulder. It was deep and undoubtedly painful, but not fatal if it could be properly taken care of. Mark was no doctor, but he could see that what he had to fear was the danger of infection, plus weakness that would result if the bleeding was not stopped in a hurry. He looked around and spotted the telltale line of dense vegetation that indicated one of the many postglacial streams flowing down out of the mountains and across the great plain. Tlaxcan's wound should be cleaned, and for that he would need water, but the stream was at least half a mile away. Mark again looked closely at the wound, and saw that it had stopped bleeding for the present. He signed for Tlaxcan to keep still, and then built a quick fire that caught more easily than had his first such attempt.

Tlaxcan watched with avid interest, taking puzzled note of both Mark's matches and his sharp metal knife that folded so miraculously in and out of itself. Mark cut a strip from the flank of Tlaxcan's kill and broiled it on a stick. Acting on a hunch, he also collected some of the wolf-thing's still-warm blood in a crude container he fashioned out of skin and gave it to Tlaxcan. Tlaxcan gulped it down with obvious relish, and then ate the meat that Mark had cooked for him.

Mark let him rest a few minutes and then judged that he was strong enough to make it to the stream. He put out the fire and got himself under Tlaxcan's good right shoulder, lifting him up. Not a sound came from

Tlaxcan's lips, not even the whisper of a moan, although the pain must have been terrific. Taking it easy, Mark supported him as they slowly walked the long half-mile and then lowered him to the ground again by the banks of the stream, which was large enough to qualify as a small river.

Tlaxcan's shoulder was bleeding again, but that couldn't be helped. A little bleeding wouldn't hurt, probably, and would even assist in cleaning the wound. Mark carefully washed it out with the ice-cold water, which stopped the bleeding in short order, as the veins and muscles contracted with the cold, permitting the blood to coagulate. He took out his handkerchief, which was still clean, and folded it into a bandage which he placed over the wounded shoulder. Then he tore a long strip from his shirttail, and after some difficulty, tied the bandage in place.

It was now early afternoon, and Mark judged that it would be unwise to try to move farther that day. He spent the afternoon in rigging a lean-to shelter and building a fire, and then sat down by Tlaxcan's side. Tlaxcan had not moved, but now his color was better and most of the tenseness had gone out of his face. He dug into his skin pouch with his good arm, took something out, and handed it to Mark.

For a moment, Mark did not understand what the thing was. It was one of those common, ordinary things that we become so used to seeing in one form that we do not recognize the same article when it is made out of something else. It was a length of some sort of organic material, about six feet long, with a curved bit of bone or ivory attached to the end.

Mark hesitated, puzzled. Tlaxcan pointed to the gurgling waters of the little river, and then Mark got it. The thing was a fishing line! He hadn't thought of fish before, but the streams must be full of them. He smiled. Fishing was something that he was an expert in, and it was nice to know that there was at least one thing he could do as well as a savage who had had the ill luck to be born many thousands of years before the blessings of civilization.

Mark examined the fishhook and decided that it was made of ivory. It was excellently constructed, sharp and with a definite barb, and it was fastened to the line by tying the line through a hole punched in the ivory, in the fashion of modern fishhooks. Mark looked at the soft river earth and considered digging for worms, but changed his mind and caught a grasshopper instead. He put the grasshopper on the ivory hook and wandered down the riverbank until he came to a beautiful dark pool behind a large rock that blocked the current. The pool was clear and cold and deep, and it had fish written all over it in letters that fishermen of any age could read without difficulty.

He dropped the line in and got an instant, thrilling strike. He yanked the line, felt the lithe, tugging pull at the other end, and knew he had a fish. He could not help thinking of how much Doctor Nye would have enjoyed a chance to fish in this paradise—how hard it was, even now, to realize that his uncle was far, far away, cut off from him by the gulf of centuries, in another world that in a sense was yet to be born.

Mark landed the fish after a brief fight, and was faintly surprised to find that he recognized the fish at once. If he was expecting some strange marine monster of the type so dear to the hearts of writers of lurid prehistoric fiction, he was disappointed. The fish was a perfectly ordinary salmon, although a beauty that must have weighed close to four pounds. Mark broke the fish's neck and cleaned it speedily with his knife. It was the work of but a moment, since salmon have no scales and are an easy fish to clean.

Mark started back to Tlaxcan, the fish held proudly in his hand. He realized that he was beginning to learn, in a way he would never forget, the first law of primitive life: you had to eat, and getting and preparing food took a lot more time than it did when all you had to do was to stroll into a restaurant and order a meal. It almost seemed to him that since he had stepped out of the space-time machine—and he had come out in the first place in search of food—it had taken every single minute of his time just to stay alive. If you weren't hunting something, then something was hunting you. Mark shuddered, remembering the horrible Neanderthals who might even now be lurking behind every bush, every rock, hidden in every twisted shadow . . .

He cooked and they ate the delicious salmon, and then passed a peaceful night in the lean-to. With the coming of the dawn, Tlaxcan was on his feet again and amazingly ready to go. Mark watched his companion with envy. He must have a constitution like an ox. Mark remembered his steel-hardness when he had supported him the day before. With a wound such as he had received, he should have been helpless for days, but here he was almost as good as new.

Side by side now, the two struck out for what was, to Mark, an unknown destination. He took careful note of their direction, so that he would not hopelessly lose the space-time machine. He and Tlaxcan were still moving almost due east, skirting the mountain foothills, and going directly away from the valley of the Neanderthals.

The warm, sun-drenched days passed, and with them the bitter-cold, mysterious nights. Mark and Tlax-can walked on across the great plain, detouring twice to get around great green lakes carved out of solid rock by the retreating glaciers. Mark could still see an occasional glitter far to the north, and he was convinced that it was indeed the last of the glacial ice, an isolated section, probably, since vegetation had already come back on the plain, and pines dotted the mountain foothills. He made up his mind to get a good look at the ice if he ever saw an opportunity. It would be a real thrill to be able to look down on the vast ice sheet that so recently had covered most of Europe, and which even in 1953 had not completely disappeared. Few people realized, in 1953, that they were not yet altogether out of the Ice Age. Enormous sheets of ice, thousands of feet thick, the remnants of those which had licked out across the world, still crushed the earth of Greenland and Antarctica in modern times. The ice was not gone, and it was a safe bet that it would come again, as it had come before, reaching back into the lands where it had been foolishly forgotten.

Mark did not waste this precious interlude of time, but rather employed it to learn Tlaxcan's language as best he could. It was out of the question, as well as impractical, to try to teach Tlaxcan English—not because Tlaxcan was stupid, but because English was an impossibly difficult tongue to learn in a hurry, as well as being quite useless in 50,000 B.c. Tlaxcan s language was simpler, although by no means easy. There were not many words, but each one had a different meaning according to the way in which it was said. Mark was handicapped by not having any books to learn from, nor any organized rules to help him, but he made slow progress and began to make himself understood in simple sentences. For one thing, he learned what Tlaxcan had been doing out on the plain when he had been attracted by the strange sound of Mark's shots. Tlaxcan had been scouting for the quaro herds, on which his people placed their primary dependence, when they could get them. Tlaxcan said that he had failed to find the quaro herds, so they couldn't have been bison, reindeer, or horses, all of which they had seen in profusion. From his description, Mark got an impression of a mighty elephant of some kind, and, putting two and two together, Mark thought he knew what Tlaxcan had been after. Mammoths!

As they went on, Mark at last had some time to think. Given a little chance to rest, his imagination went busily to work. Where, exactly, was he? What, in modern times, had become of the great plain on which they were walking? As nearly as he could figure it, they were somewhere near the modern line between France and Germany. It was a little frightening to think, as they walked along under the sunny skies, that all the teeming millions of France and Germany were as yet unborn, dust and less than dust. No man in the world had yet heard the name of Napoleon, or of Hitler. Mark looked about him, wondering. What history would be written, how many men would die on this grassy plain before the end of time? In his mind's eye, as he walked through the grass in the dawn of man, he could almost see the great plains twisted with ugly slit trenches, the mighty guns, yet uninvented, belching flame and death from black muzzles.

Mark could not help thinking, there in the sun with Tlaxcan at his side, of the relativity of it all. Here he was, in 50,000 B.c., and the beautiful plain was, as he knew all too well, deceptively deadly. Wild animals roamed through its grasses in dense herds, and the hideous Neanderthals prowled its surface in wicked packs. It was no place to be alone; it was hard and tough and demanding. But would almost fifty-two thousand years of civilization make it any safer? He doubted it. No matter what frightful danger waited for him beyond the smoke-blue horizons, he knew that there were at least no atom bombs to vaporize his body into nothingness.

Mark walked along beside Tlaxcan and reflected upon what a vast difference a companion made. When he had been alone, this savage world had been an impossible one. He had been lonely and afraid. But now he had a friend, for that was how he thought of Tlaxcan now. Tlaxcan was no longer a mysterious being from the dawn of time, nor was he an illiterate savage. He was Tlaxcan. A man who laughed a lot in a world that was no laughing matter, a man whom Mark was proud to have at his side. He had a friend, Tlaxcan, and he could depend on him. That made all the difference, he knew, the difference between living and dying. That was the secret behind the survival of the fittest. The fittest did indeed survive, but he was fittest because he had the one secret that made him a man—the secret of friendship. It was co-operation, one man helping another man, that had enabled man to survive in a harsh world. Alone, man was little more than an animal. But together, united, he was king. They seemed to know that much in 50,000 B.C. Had they forgotten, Mark wondered, in 1953?

On the fifth day, just as the blood-red sun was gently sinking to the far horizon, Mark and Tlaxcan left the whispering plains and walked up through the foothills and into a secluded mountain valley. The valley narrowed as they continued along it, until it was barely wide enough to hold the foaming mountain stream that rushed through it, and in the distance they could hear a roaring thunder as of a mighty storm.

After a short time, the valley turned sharply and they rounded the corner on a well-worn path that ran to one side and slightly above the swiftly flowing water. They rounded the corner—and there it was. Mark stopped in his tracks. He had never seen this place before, but he knew instantly, without question, that they had come to the end of their journey.

Mark Nye had known beauty before. He was no calf-eyed weakling who was forever gasping about the beauty of it all, nor did he often speak of beauty in any form. But beauty he had known nonetheless—the beauty of sunrise in the New Mexico mountains, the beauty of old Rome at night when the ghost legions marched, the lonely beauty of frosted city lights in the early morning when the city slept. He was no stranger to beauty, but he had never seen the equal of the sight which now confronted him.

In the blue distance at the head of the valley, a mighty torrent of water thundered down from the mountains in a spectacular waterfall. It smashed down for fully one hundred feet into a rock basin, where the white clouds of spray were turned all the colors of the rainbow by the setting sun. From the basin, the water boomed down in a lovely double cascade, one stream on either side of the basin. The cascades dropped into a deep, bubbling pool, and from the pool streamed the water that flowed through the valley, cold and sparkling in the last light of evening.

Thick green grass covered the valley floor like a soft carpet, and clumps of sweet-smelling pines grew around the edges and up into the surrounding hills. The air was incredibly fresh and clean, with just a hint of campfire smoke and the delicious smell of roasting meat. Under the pines, and spread somewhat up into the hills, were large and well-constructed lean-to structures, built with a framework of poles covered with great cured skins. In front of the lean-tos, small fires blazed cheerily.

Upon the rock ledges that broke out from the hillsides, Mark could see the dark openings of a labyrinth of caves. Within the depths of the caves, but not too far from the entrance, fires crackled with heat and light.

The valley was not silent, but neither was it noisy. A soft roar from the cascades in the distance filled the air with a gentle backdrop, and there was the humming sound of many voices. From one of the caves came the sharp tick-tick of rock striking against rock.

The valley seemed to be filled with people—not that there were really so many there, certainly not over sixty or seventy, but it was the most people Mark had seen together in a long time. There were men, women, and children, young and old. The men and the women were dressed in furs, like Tlaxcan, and the children, for the most part, were as innocent of clothing as the

in this strange world. His future was here with these people, or else he had no future at all.

He looked at Tlaxcan, quiet by his side. Had he led him into a trap? Had he taken Mark back to his own people as a prisoner, a slave, a trophy of the hunt? Mark didn't think so. Although as yet they could not talk fluently to each other, he had gotten to know Tlaxcan pretty well during their trip across the plains. Tlaxcan was young, possibly no older than Mark, although he seemed adult in every way. He had a refreshing and genuine habit of laughing wholeheartedly at little incidents; everything, to him, had a humorous side that he invariably sought out to laugh at. But it was not a stupid laughter, the laughter of an idiot who knew no better. It was the laughter of a man who lived in a tough, hard world and had learned that it was wiser to laugh than to cry. Behind Tlaxcan's laughter, deep in his dark eyes, there was cold steel. He was not a man to fool with, and, if Mark was any judge, he was not a man to betray a friend.

Once again, he put his trust in Tlaxcan. He was not sorry. At once, as though sensing Mark's decision, Tlaxcan stepped forward, between Mark and the oncoming warriors.

"Orn," Tlaxcan said clearly, pointing at Mark. Then he spoke again, too rapidly for Mark to catch what was said. The Cro-Magnons slowed their pace, but they kept coming. "Tlan!" ordered Tlaxcan coldly. "Stop!"

The warriors kept coming. Tlaxcan slipped an arrow from his quiver and fitted it to his bowstring. He drew the bow taut, and it was clear that he was not bluffing. He was ready to shoot. The warriors stopped. At the time, Mark wondered greatly at the fact that Tlaxcan was quite evidently ready to put an arrow through a lifelong friend for the sake of someone he had known for a few days, but the explanation was simple enough. The band of Cro-Magnons was seldom together in the valley as a unit, each extended family group following the herds alone for most of the year. The warriors who confronted them now were not members of Tlaxcan's immediate kinship group, and so were not close to him. Probably he had not seen them twenty times in his life. They were known not to be enemies, but that was all. They were not his personal friends.

For a long moment, the tense scene held. Then five more warriors came up and arranged themselves behind Tlaxcan. Tlaxcan greeted them by name, and they were obviously friends of his. They looked at Mark coldly, but offered him no harm as long as he was under Tlaxcan's protection. Mark began to realize that helping Tlaxcan when he had been in trouble was the smartest thing he could have done. Strangers around here were clearly presumed to be enemies unless they could prove otherwise in a hurry. They were declared guilty until proven innocent—if they had time to prove anything before someone ran a spear through them. With Mark's halting command of the language, he would not have had a prayer without Tlaxcan.

The ten warriors milled about uncertainly for a moment, and then went back the way they had come. Mark breathed more easily again. He turned and smiled at the five friends of Tlaxcan and, after Tlaxcan had explained the situation to them, several of them smiled in return. They did not, however, welcome Mark with open arms. Mark knew that getting himself accepted into this tribe as an equal was apt to prove something of a job. Desperately, he wished that he could talk with these people in a way that would make them understand that he meant them no harm.

"I am your brother," he said in their language. "I come in peace." That was the best he could do, and he saw Tlaxcan smiling at his accent.

Four of the warriors did not respond, but the fifth, an older man of perhaps forty years, iron-hard but with streaks of gray in his long hair, came forward and put his hand on Mark's shoulder, much as Tlaxcan had done. "I am Nrani," he said in a friendly voice. "I am Tlaxcan's brodier. You are Tlaxcan's brother. I am your brother."

Mark nodded, wishing fervently that he knew how to say "thank you" in Cro-Magnon. The term "Cro-Magnon," of course, was not the name that these people used in referring to themselves. They had been named the Cro-Magnons because the original scientific discovery of five modern-type skeletons had been made at the rock shelter of Cro-Magnon in the French village of Les Eyzies during the late 1800's. The Cro-Magnon peoples themselves, living as they did in the dawn of man, had never heard the name by which they were to be known to science. They referred to themselves as the Danequa, with the middle e pronounced as in the English "neigh" or like the a in "ate." Literally translated, Danequa meant simply "the people," which, as Mark knew, was a common practice among isolated primitive groups. Many primitive societies thought they were the only human beings in the world, all others being mere animals.

With the five warriors for an escort, Mark and Tlaxcan made their way across the valley floor and climbed a narrow trail up to one of the rocky ledges where the caves were. The sun was gone now, although there was still light enough to see by. The cold night wind was already whipping through the hills, and in the distance the great waterfall sang its lullaby of power. The whole scene seemed to Mark to partake of the unreal, of fantasy. It was a moment sliced out of legend, the time-frozen landscape of a dream . . .

Or was it the other world, the world of 1953, that was a dream? His uncle, the space-time machine, his dog, Fang, did they really exist? Mark shook his head. It was useless to think such thoughts. He was where he was, and his problem right now was staying alive.

When they reached the ledge, no one spoke. The people there looked at him curiously, neither hostile nor friendly. They seemed to be waiting. Waiting for what? Mark soon found out.

From one of the caves there came an eerie, high-pitched whistle. This was repeated six times, and then there was a sort of chant, delivered in a rather high, rhythmical voice. Mark could make no sense out of the chant, although he thought he caught a familiar word now and then, mixed in between strings of singsong syllables that were to all intents and purposes meaningless. Finally, the chant stopped. There was a complete, hushed silence.

Out of the mouth of the cave, through the black shadows of evening, danced a painted man. Mark did not move.

The man came toward him in a strange, dancing motion. He hopped first on one foot for six steps, then on the other for six steps. As he danced, his hands and arms writhed like snakes and his head bobbed forward and backward as though disconnected from his body. Even in the fading dead light of evening, the colors of his body were startling. Arms, legs, face, chest, back— the man was completely covered with brilliant paints. The paint was striped in thin series of sixes, each series composed of red, brown, black, white, gray, and green. Shells and ornaments of bone and ivory adorned the painted man as necklaces, arm bracelets, and leg rattles. They clicked and whirred together with the motion of his body, and in the silence they reminded Mark of nothing so much as the warning whirrrr of a rattlesnake.

The man was frightening, but Mark was not as unnerved as he would have been had he not seen similar painted men before. He knew the grotesque dancer coming toward him was much the same sort of official as the Neanderthal with the red band on his forehead had been. He was a type of person that Doctor Nye had often discussed with him, a type of person he himself had seen among the Indians. He was a shaman, popularly known as a witch doctor.

Knowing these facts was helpful. It changed the oncoming dancer from a supernatural horror to an understandable human being, one who could be dealt with. But it did not change the fact that Mark was skating on very thin ice and had to watch his step. Knowing that the painted man was a shaman did not dispose of him—and shamans could be dangerous.

Shamans had the power of life or death.

A lot depended on the individual, as always. In common with other professional people, a shaman was a human being first and a witch doctor afterward. They were sometimes insane, sometimes subject to fits, sometimes not. Is the driver of a car dangerous? It depends on who the driver is, and where you happen to be. The painted man was completely unknown to Mark; he was an X factor. What should he do?

Once more, Tlaxcan came to his aid. He touched Mark on the arm to reassure him and smiled his quick and ready smile.

"Orn," whispered Tlaxcan. "Do not be afraid."

Mark smiled back, but his smile was a little shaky. That word "orn" was apt to be used pretty loosely from his point of view. The painted man coming toward him might be lots of things, but if the expression in his eyes was friendship, then Mark wanted no part of it. It looked like the sort of friendship a vampire might feel for its victim.

The painted man stopped. Tlaxcan at once began to talk, speaking too rapidly for Mark to follow him. The shaman talked back, his voice a trifle high for a man's, although not abnormally so. Then Tlaxcan started in again, and now Mark was able to catch enough of the words to understand the general drift of the conversation. Tlaxcan elaborated the details of how Mark had saved his life, and then recounted the story of how he had first come upon Mark on the plains. He spoke in awed tones of the reindeer that Mark had killed without any weapons except a small knife, and Mark realized that Tlaxcan was speaking the literal truth so far as he knew it—he probably regarded the .45 as a magic charm of some sort, or at most as a clumsy fist-ax. Tlaxcan told about the amazing knife that was not made of stone, and he spoke of the red flower—fire-that Mark had kindled by magic.

The shaman was visibly impressed, although he tried not to show it and muttered something to the effect that all that was old stuff to him and he could do it himself if he really wanted to. Tlaxcan did not contradict him, but he was plainly skeptical.

The shaman turned to Mark. "Come," he said, and his voice was not entirely without fear. Mark suddenly realized that this shaman was doing a very brave thing, from his own point of view. To him, Mark had just been represented as no mean witch doctor himself, and for all he knew he might be out looking for trouble. Mark relaxed a little, and after another reassuring smile from Tlaxcan he followed the shaman back across the ledge toward the cave.

The waterfall moaned and boomed in the distance, and night had fallen like black snow in the valley. Despite Mark's realization that the shaman was uneasy, he was none too confident himself. As he followed the painted man into the dark cavern, Mark could not help wondering whether or not he would ever come out of the cave again—alive.

The cave was large, roomy, and dry. They turned one corner, and then proceeded down a long, straight tunnel to where a small fire burned in a tiny chamber. The fire, Mark noticed, fed on dry bones, not wood— a logical enough fuel source in a land that was somewhat short on wood. The painted man did not stop, but continued on into a larger chamber beyond. It was dark, with only enough light coming in from the flickering fire outside to gray the air and throw great twisting shadows on the walls.

With startling suddenness, things began to happen. The shaman, as far as Mark could tell, stood quite still in the center of the chamber. The chamber was otherwise empty. But weird songs, chants, and screams filled the air, coming from the ceiling, the floor, the corners. Voices came frpm nowhere at all, and not only voices of humans. Bison snorted, horses nickered, lions roared, and grim trumpetings that could only have come from mighty mammoths echoed through the cave.

Mark shivered. In spite of himself, he edged back toward the light. Something snarled right behind him and he stopped abruptly. Ventriloquism, his mind whispered, but he was growing nervous nonetheless. This shaman knew his stuff; he was good.

An eerie, violet light filled the cavern. Mark was startled. Radioactive rocks? Some kind of glowing mineral? He didn't know, but he could see that the painted man now had a long coat on. And in his hands was something large, white, and gleaming. A skull.

Not just a skull, either. A monster skull, with two huge curving tusks of ivory. The thing was enormous. Mark wondered wildly how in the world the shaman was holding it up, and decided that it must be suspended on a rope of some kind that he could not see in the gloom. The shaman looked straight at him, his eyes gleaming.

"Mark," he intoned, his voice like blue ice in the empty chamber. Then his eyes looked down at the skull in his hands. "Quaro," he said distinctly. "Mammoth."

Mark watched intently. The shaman took his hands off the skull and it hung whitely in mid-air. A rope, Mark reminded himself in desperation, a rope. A knife appeared in the shaman's hand as if by magic, and he whipped it around in a blazing arc into the skull of die mammoth.

The skull disappeared. That was all. Disappeared.

Mark gasped, and realized for the first time that he had been holding his breath. He thanked his lucky star that he knew enough anthropology and Indian lore to interpret what he had just witnessed. Unless he was very much mistaken, the import of what he had seen was simple enough, in theory at least. He had come into the tribe, seeking status as a member. Very well. The tribe, naturally, wanted no weaklings, no incompetents. Mark had to prove himself first. How? In a way that would leave no doubt of his manhood. He had to kill a mammoth.

That, Mark knew, was easier said than done. It was out of the question that he could kill a mammoth with a pistol shot, even with a .45. He did not know how these people went about hunting the giant monsters— surely not just with a bow and arrow—but he could only hope that they didn't do it alone; he would need plenty of help. He had a feeling, however, that he would not be asked to do anything impossible. He simply had to show that he could do what any other man of this time could do—no more and definitely no less. That, too, he knew, would take some doing.

The shaman led the way out of the dark chamber, back into the small cave room where the fire was. The show was over. Even in 50,000 b.c., it appeared, magicians had found that magic worked better in the dark where no one could see too clearly. But it had been a spectacular performance, judged by any standards. Mark noticed that the shaman was having trouble holding back a satisfied smile. He was evidently well pleased with his night's work.

The painted man, now dressed in a heavily decorated coat, placed his arm on Mark's shoulder in the

Danequa gesture of friendship. "Qualxen," he said, giving his name. Mark realized that he was being honored, and smiled his appreciation. lie returned the gesture, giving his own name despite the fact that Qualxen obviously already knew it.

There was an awkward moment of hesitation, and Mark figured that the shaman was waiting for a coun-terdemonstration of power. The ceremony was over, so to speak, and now it was just a case of two magic men being together. Did Mark perhaps have a trick or two of his own up his sleeve?

Mark did. Furthermore, he would do his trick right out in the open, in the light, without mumbo-jumbo. He fished out his box of precious matches and took two matches out of the box. He thought fast. It wouldn't do to just strike the matches; the essence, the vital part, of any magic trick lay in the build-up you gave to it. If a magician just walked calmly out onto a brightly lighted stage and proceeded to saw a woman in half, chances are that the audience would be bored stiff, even if he really did saw a woman in half. But let the house lights dim, let the magician chant a strange song from a nameless land, let the weird music cry and moan in the orchestra pit—that was different!

Mark decided that he had to have a chant, at least. Any chant in English would do, since Qualxen would not know what he was saying. He thought of a football yell, but that didn't sound right. Finally, he selected a rime that had just the rhythm he desired. Mark frowned terribly and made passes at the air with his hands. He moaned and clapped his hands six times—use of the Danequa magic number wouldn't hurt any, he supposed. Then, suddenly, he stopped dead and thrust his face at Qualxen.

"'Twas the night before Christmas," Mark whispered in an eerie tone of voice, "and all through the house—"

The shaman jerked backward fearfully. Truly, this was strong medicine! "Not a creature was stirring," moaned Mark terribly, "not even a MOUSE!"

With the last horrible word, Mark quickly lifted his hands to the level of Qualxen's face and snapped the two matches together. There was a sharp crack and a puff of flame. Qualxen stood his ground, but it was easy to see that he was terrified. The red flower, fire, out of nothing! Contemptuously, Mark blew out the matches and tossed them into the fire.

Qualxen recovered his composure and grinned delightedly. "Orn," he said, again touching Mark on the shoulder. "Orn!" Qualxen knew a powerful shaman when he saw one, and he wanted to be on his side. Mark knew that he had made a powerful ally in the camp of the Cro-Magnons—and, besides, he found himself rather liking the intriguing Qualxen.

Qualxen led the way back through the cave, and as they drew nearer the entrance Mark felt his high spirits begin to desert him. Whether Qualxen was friendly or not, that grim ceremony in the dark cavern had been in dead earnest. It would take more than a trick with a match to bring down the monster mammoth.

It was night now, a cold night frosted with stars. The icy wind sighed across the valley floor and touched Mark with chill fingers. In the distance, the great waterfall thundered forever down its silver cascades. And beyond that—was it only Mark's imagination? The deep trumpetings of gigantic mammoths!

found a fur covering that had been left in the cave for him. He wrapped himself up in this and was quite comfortable.

He could not be sure, but he thought that this cave —which was very small, little more than a deep recess in the rock—was the one from which he had heard the whinings and growlings of the wolf-dogs earlier. He sniffed the air, and there was no doubt that something had recently occupied the cave. He hoped with all his heart that it had been nothing more dangerous than a dog, and that it wouldn't take a notion to come home sometime in the dark hours of the night.

Mark was very tired; he had not realized how tired he was until he stretched out on the cave floor with the warm fur over him. He took his .45 from its holster, placed it within easy reach and closed his eyes. The ways of men are indeed odd, he thought sleepily . . . A few short days ago, he would have thought anyone crazy who tried to tell him that it would be possible for him to go back through space-time to the beginnings of man and calmly go to sleep, without fear and with an untroubled mind. And yet he found himself relaxed and trusting toward his new-found friends. The Danequa, he was sure, were not a treacherous people. He was safe in their hands—safe, at least, from cowardly sneak-attacks. When these people felt like arguing, they would do it in the open. And here, finally, he need not worry about the ghastly half-men, who prowled like fantastic accidents through the night lands of the Ice Age . . .

Mark slept and dreamed. He was grateful for the sleep, but it would be long before he was able to forget his dream.

Through the gray twilight world of sleep, in a world without color of any sort, a man ran desperately. He had been running for a long time, and he was very tired. His lungs ached, and even in the cold air sweat covered his body like a film of moisture. His feet were cut and bleeding. The man was dressed in furs, but Mark knew him. The man was himself.

Behind Mark, almost touching his weary feet as they pounded across the gray earth, the half-men screamed and growled hideously. Mark did not dare to turn and look at them, but he knew that they were there. The Neanderthals neither gained on him nor did they lose ground. They came on untiringly, always exactly the same distance behind him.

Where was he going? Mark looked around him, sensing that he knew this country somehow. He had been here before. Behind him, the low pine-covered foothills merged into the mountains, with their snow white against the gray sky. Between the mountains was a valley—and not the valley of the Danequa, with its green grass and beautiful waterfall. A ghastly valley, a nightmare valley . . .

To his right, a gray field undulated to the horizon, gray grass shimmering in ghost-waves under a supernatural wind. He could see the wind—it looked like gray smoke. Far away, a glimmer of lighter gray. The ice sheet. And ahead of him, a great sphere, waiting on the plain.

The space-time machine.

Gasping for breath, the half-men right behind him, Mark threw the gray switch in the side of the machine. The circular door hissed open, and Mark plunged inside. He closed the entry port behind him, catching one

Neanderthal's hand in the closing section. The hand was cut off and dropped to the floor, gray brute fingers still wiggling.

Mark lay on the floor of the space-time machine, fighting to get his breath. A tremendous wave of relief flooded through him. He was safe! He had only to set the controls and step out to greet Doctor Nye, and Fang, and be home again in New Mexico. He laughed, hysterical with relief over his narrow escape.

Something laughed back at him. He wasn't alone.

Mark jerked to his feet and then recoiled in horror. There was a Neanderthal inside the machine with him, the biggest Neanderthal he had ever seen. He was fully nine feet tall, and his great hairy body almost filled the sphere. The smell of the half-man washed against his nostrils. Mark screamed frantically. The Neanderthal's monstrous hand reached out for him, the hairy fingers with their dirty, clawed finger nails touched him—

Mark woke up with a start. There was a hand touching him, but it belonged to no Neanderthal. It belonged to Tlaxcan.

"You have been in the Land of Shadows," he said, smiling. "You are back now."

Mark got to his feet, rubbing the sleep out of his eyes. Pale rays of the early morning sun lighted up the world, and the fears of the night dissolved in their warmth. Consciously, Mark did not place any faith in dreams. They were what they were—dreams, with no special meaning or significance. But subconsciously, deep within his mind, he found his nightmare hard to forget. He was shaken, and it was no easy matter to thrust his strange dream from his thoughts.

It was good to be with Tlaxcan again, and Mark went out with him into the life of the Danequa valley. The booming waterfall was more beautiful than ever, gleaming in the morning sunlight, and the scent of pines was bracing in the fresh air. Mark followed Tlax-can to his own cave, a large, roomy cavern high on another ledge. There he was surprised to find that Tlaxcan had a family. It was curious that he had always thought of his friend as single, but now that he paused to think about it, he remembered that most primitive peoples married while quite young, out of economic necessity. A man had to have someone to make his clothes, cook his food, keep his home. There were no servants in this dawn world, and most of a man's time was taken up with hunting and fighting.

Tlaxcan's wife greeted Mark shyly, touching her hand to his shoulder in greeting. She was attractive in a clean, healthy way, and obviously devoted to Tlaxcan. Her name, Mark learned, was Tlaxcal, which was the Danequa feminine form of Tlaxcan. This seemed curiously wrong to Mark, and for a moment he was at a loss to understand why. Then he had it. In English, "Al" was a man's name, while "Ann" was a woman's. It seemed funny to hear them reversed, but no funnier, he knew, than the English version would have seemed to the Danequa.

Tlaxcan had a son too. He was a hearty, handsome child of three, and his name, with wonderful economy of logic, was Tlax. He toddled fearlessly up to Mark and tried to reach up to place his small hand on Mark's shoulder. Mark bent over to accommodate him, and grinned. As a rule, he was not overly fond of young children, but Tlax was one in a million. He was thoroughly cute, and Mark fell for him at once.

They breakfasted on roasted meat and berries. The meat was pungent with strong flavor, and Mark guessed that it was bison. The berries, he noted ironically, were the same red variety that he had passed up when he was so hungry before, because he had feared that they might be poisonous. They were delicious.

When they had eaten, Mark sat back and talked as best he could. He felt very much at home, and joined heartily in the good-natured laughter at young Tlax, who was industriously trying to pull back the string on his father's bow, which was almost as big as he was. It was hard to reconcile Tlaxcan, the happy family man, with the grim-eyed savage, ready to kill, that Mark had first met on the grassy plains. It showed, if nothing else, that first impressions were apt to be very misleading. Mark felt that he had known Tlaxcan all his life; and he knew with sudden certainty that he would never have a better friend, nor a finer one, anywhere.

Tlaxcal, while avoiding looking at Mark directly, had been examining his clothes with some interest. Mark was uncomfortably aware that they were very dirty, as well as being ripped and torn from the rough wear he had given them. Tlaxcal whispered briefly to Tlaxcan, and Tlaxcan smiled his approval. Mark did not have to be a mind reader to figure out that he was going to get a new suit of clothes, and once more he determined to learn how to say "thank you" in Cro-Magnon. He did the best he could with his eyes, and felt that he had succeeded in getting the idea across.

They left the cave finally, Mark smiling his farewell to Tlaxcal and little Tlax. Tlax tried to follow them down the rocky trail, and his mother came out and pulled him back, scolding him for all the world like a modern mother. Mark thought of his own mother, the mother he had hardly had time to know. And his uncle —where was he now? What did "now" mean—when was "now"? Was his uncle as yet thousands of years unborn, or was he still talking on the telephone to White Sands?

Mark walked among the Danequa, and he kept his eyes open. It was entirely possible, he knew, that he was destined to spend the rest of his life with these people. The thought did not dismay him, for it was plain enough that the Danequa, with their skin clothing sewn together by ivory needles, their artistic weapons, and their robust good humor, were a remarkable and gifted people. Mark had lived in this hard dawn-world long enough now to begin to appreciate the accomplishments of the Danequa. True, their camp in the valley with the foaming waterfall was simple and crude enough by the standards of the twentieth century. There were no towering skyscrapers, no great electric generators, no theater but the clean show place of nature. But things are seldom what they seem, and this was no exception. Which was the greater accomplishment, to invent for the first time a bow and arrow, or to develop, with all the resources of thousands of years of technology behind you, atomic energy? It was not an easy question, and Mark was far from sure how he would go about answering it.

That day, Mark met Roqan, and his wife, Roqal. Roqan was an old man as Danequa men went, perhaps fifty years of age. His hair was still dark and thick, but his face was lined and wrinkled far more than a modern man of fifty would have been. He seemed to be very

stern, and he had an old hunting scar across his forehead that made him seem fiercer than he was. Roqan frowned constantly, and was treated with great respect by everyone. When he met Mark, he examined him as he might have looked at an insect.

"What do you want of us?" he demanded sternly. "I have known your type before. You have come to steal our food and kill our warriors."

Mark returned his harsh gaze, determined not to look away. He wished desperately that he could speak the language well enough to make an effective reply to the old man, but all he could do was to stammer a reply to Tlaxcan, who answered for him with a few ideas of his own.

"My friend says that he comes in peace," Tlaxcan said to Roqan. "His only desire is to learn to be wise and good as is his brother, Roqan. He has heard of Roqan from afar."

"You He," stated Roqan flatly, but he was obviously pleased. His old eyes twinkled with delight, and Mark got the distinct impression that he was disgusted with himself for permitting his good nature to shine through. He at once wiped the pleased expression from his face and replaced it with his customary frown. But Mark wasn't fooled this time. He knew that he and Roqan would get along.

Roqal, his wife, seemed to be his direct opposite, at least on the surface. She was very plump and motherly and bubbling over with friendliness. Mark suspected that she was bubbling over with something besides friendliness, for she seemed slightly tipsy. He suspected that she was addicted to taking frequent snifters of the Danequan equivalent to liquor, a fermented berry drink aptly named kiwow. Roqal greeted him with an almost girlish giggle, and let him know in no uncertain terms that he was most welcome.

Mark saw Qualxen, the shaman, again, and he greeted him like an old friend, together with winking between-us-shamans secretiveness. Mark played along with him, and was genuinely grateful to have friends again. It made the world, any world, a much brighter place to live in.

Mark only met two people that day with whom he could not get along. One was a thin, pale man named Tloron, who, as nearly as he could understand what Tlaxcan tried to explain to him, was a holy man of some sort who had great magical powers. Evidently his power was of a different sort than Qualxen's, because there was no jealousy between the two men. Mark rather liked Tloron, but he was silent and kept strictly to himself; Mark found it impossible to talk to him. The other person who gave him trouble was an entirely different proposition. His name was Nran-quar, and he was a tall, powerful warrior who appeared to be capable of tackling a mammoth alone, without batting an eye. Nranquar was suspicious of Mark, and didn't try to hide the fact. He let it be known that he would be watching Mark in action against quaro, the mammoth, and Mark knew that he had better come through with flying colors—or else.

It was a good day, all in all, and Mark was sorry to see it end. The valley was humming with activity, and Mark understood that this was the time for tribal ceremonies. Indian fashion, these people were in isolated groups following the herds most of the year, and when they got together they made the most of it. Tlaxcan apologetically explained to Mark that he could not participate in or witness the ceremonies, because he was still technically an outsider. After the evening meal, Tlaxcan escorted him back to his tiny cave, where someone—Mark strongly suspected that it had been Tlaxcan's wife, Tlaxcal—had kindled a small fire and left enough dried bones to keep it going.

Alone, Mark sat in the mouth of the cave, wrapped in his fur blanket, and watched the black shadows of night creep through the valley, soaking up the fading light, and clearing the way for the cold night wind sweeping down out of the north. The stars dusted the dark sky with frozen pearls, and the waterfall muttered and boomed in the distance.

It was infinitely lonely, all the more lonely now that he had once again tasted friendship and the warm glow of human companionship. The Danequa—men, women, and children—were gone from the vicinity as though they had never existed, leaving only the dark pines and the moaning wind behind them.

Fires flickered into life far across the valley, near the shores of the deep pool at the foot of the waterfall. Alone in the silence of the night, Mark heard the ceremonial drums of the Danequa take up their rhythmic chant. The throbbing drums were felt, rather than heard, against the roaring backdrop of the mighty cascades. And then came the singing, a weird chorus of plaintive cries, with deep voices mixed with high ones in a never-ending flood of sound. There was no harmony, and the rhythm of the voices was different from the rhythmic beat of the drums.

Sad, lonely, wistful, exciting—the sounds of the ceremony were carried by the sighing winds across the valley of the Danequa to where Mark sat alone. Savage it may have been, and primitive it certainly was, but Mark would have given his heart and soul to be there with them now, dancing under the stars.

A silver moon climbed high into the sky of night, and still the drums played on, and the singing sobbed across the valley floor. Mark had hoped that the ceremony might end, and someone might come by and just say hello before morning—but no one came. This was a night for the Danequa, and he was not of the Danequa.

Finally, unable to watch the fires any longer, but still not tired, Mark crawled on into the tiny cavern and stretched out on the floor under the robe. He closed his eyes, but he could not sleep. The rhythmic pounding of the drums, mixed with the humming roar of the waterfall, marched in through the cavern mouth and thumped against his ears. The singing filled the cave, and Mark knew that he had never been so lonely in his life. He thought of home, as lonely people do, and he was acutely aware that home was almost fifty-two thousand years away.

Then another sound came into the cave, a different sound. For a moment, Mark could not place it. It was something of a whine, and yet it was something of a snarl . . .

Mark leaped to his feet, wide awake, the .45 ready in his hand. His first thought was of the half-men, and he felt himself shuddering. He would kill himself before he would surrender to those monsters again, but he would take a few of them along with him. He waited, holding his breath. Nothing happened.

The sound came again, and Mark peered cautiously at the mouth of the cave. He couldn't see anything. He took a long stick with his free hand and stirred up die fire. The circle of light expanded, slowly. There, a dark shadow! Mark took careful aim, but held his fire.

"Who is it?" he called. "What do you want?"

No answer. There was only the night, and the moon, and the shadows.

"Answer or die!" Mark hissed, his finger curling on the trigger.

There was a low whine. The shadow moved and came into the circle of firelight.

"Well, I'll be darned," Mark muttered in relief.

The thing was an animal. More than that, it was a dog. At least, it looked so much like a dog Mark could not see any difference. He was almost full-grown, a brownish-gray in color, and looked a great deal like an Arctic husky. He was lying flat on his belly, his head cocked to one side in a questioning attitude, his bushy tail wagging hopefully.

Mark remembered at once the sounds he had heard coming from this cave when he had first arrived among the Danequa, and it did not take him long to put two and two together. He did not believe that the Danequa had domesticated the dog, in the sense of keeping them and breeding them in captivity. But it was certainly possible that they permitted some of them to hang around the camp, living in empty caverns, to feed on the scraps and thus keep the place clean. No doubt they even petted them occasionally, and perhaps played with the puppies. At any rate, this dog looked anything but vicious. He seemed to be pathetically eager to make friends.

friendly relationship between Mark and the dog; they had never seen a pet before. But they accepted it as they had accepted Mark himself. Different people behaved in different ways, and that was all there was to it. Nranquar was still suspicious of Mark, and having Fang around didn't help matters any, but he was the only one who seemed to care one way or the other.

Then one day it happened. One of the scouts, out on the same duty that had first taken Tlaxcan to Mark, came back to camp with the long-awaited news. The mammoth herd had been sighted!

The camp was thrown into great excitement over the information, and at once preparations for the hunt were begun. The primitive equivalent to K-ration, dried meat pounded and mixed with berries, then sealed with animal fat, was made ready for use. Qualxen went into action to contact the supernatural, and brief ceremonies got underway. Mark for the first time appreciated how much time was taken up by the Danequa in their almost endless ceremonies, but the ceremonies gave to them a confidence that was well worth the time invested. On a tough job, it helps for the worker simply to believe that the job can be done.

The men were armed with lances, harpoons, bows and arrows, and sharp cutting knives. The women and children prepared noisemakers of various sorts, and loaded up on robes which they would flap. Mark carried his .45, and was prepared to use it if he had to, but he was not under the illusion that he could kill a mammoth with a pistol. In addition, he carried one of TIaxcan's spears, and he was determined to prove himself on this hunt.

He had to prove himself, he remembered grimly.

The camp moved out through the valley and hit the long trail. The quaro herd had been sighted due north, on the edge of the retreating ice sheet, about fourteen hours distant. Men, women, children—the whole tribe went. The mammoth meant food, shelter, clothes, and many other things for the whole village, and it took the whole village to bring one down. One hunter, no matter how able, could not possibly handle a mammoth. It would be like hunting an elephant with a slingshot, a practice which does not work very well outside of the jungle movies.

It was broad daylight when the Danequa moved out, and once more Mark found himself on the great plains with their waving grasses and millions of brilliant flowers. But it was different this time; he was no longer alone, he was part of a team, and the world held no terrors for him now. He might win or he might lose, he might live or he might die, but he could face what was to come with a steady heart. Part of it was due, of course, to the friends that walked at his side—but part of it, too, was due to Mark himself. For Mark, subtly and almost unknown to himself, had changed. It is doubtful that his friends in 1953 would have recognized him now—a young, bronzed savage, spear in hand, long hair held in place by a thong of bison hide, his body covered with the warm furs that had been made for him by Tlaxcal, a fierce wolf-dog at his side. Mark had been aged by more than time, and he was hard as only a hard world can make a man, with a confident, even look in his eyes.

All through the day the colorful procession moved through the dawn of time. The men were painted, even Mark having consented to a couple of stripes of green across his forehead and arms. In fact, he remembered with a smile, he had been grateful to Qualxen for offering to paint him—thus quickly did his values change. He even wore a tiny medicine bundle on a string around his neck. There was nothing in it but a tooth and a small stone, and he assured himself that he did not believe in its powers. He wore it, however.

When in Rome, do as the Romans do. He had almost gone to Rome—what would have happened to him there? Would his uncle ever see that fabled city in the time of its glory? He thrust the thought from his mind.

The sun drifted down to the rim of the mountains, and the evening shadows crept across the land. Mark was astounded when they saw a herd of bison in the distance, so vast that it was like a black flood on the land, and when they broke into a run, the dark waves were set into motion. There must have been thousands upon thousands of the beasts, and now Mark could well believe the stories of the early American West about herds of buffalo that stopped trains. But the Danequa were not after buffalo now—they were out after bigger game.

Just at nightfall, they saw a large herd of horses galloping across the grass, racing the shadows. Mark could not help thinking of how much easier life would be for the Danequa if they could just see the possibilities of using the horse as a riding animal. But evidently the idea had never occurred to them, and they marched along on foot within a hundred yards of the finest riding animal the world had ever known. How many other such opportunities, Mark wondered, were under our very eyes in 1953, obvious enough if someone could only put two and two together in the right way?

Through the night marched the Danequa, under the stars and under the moon. They seemed to have an infallible sense of direction; there were no landmarks that Mark could see. Somewhere in the night, he knew, was the space-time machine. It was there, to the west, to his left. It was ready to go now, if it was in good condition still. All he needed to do was to walk to it and get in. But that was the catch—walking to it. The Neanderthals would be watching from their valley of death, and he could never get through them alive.

Almost, he fancied that he felt the cold eyes of the half-men on him now, as he walked on across the plains.

In the tricky light of false dawn, which faintly illuminates the earth an hour before the true dawn of sunrise, the scouts located the quaro herd. Mark had not yet caught a glimpse of them, but he could hear them. Their trumpetings, elephant-like, coughed through the cold air surrounding the ice sheet, sending shivers along the spines of the bravest of men.

Like a well-drilled team, the Danequa went into action. Every person knew his place—knew what to do and how to do it. The old men stationed themselves at the foot of a jagged cliff that offered a drop of fully one hundred yards to solid rock below—a product of the great earth cracks and fissures which resulted from the passing of the glacial ice. The Danequa had obviously used the cliff before, because Mark could see plenty of bones around. Huge bones . . .

The women and children, armed with all sorts of noisemakers and robes, spread out behind rocks leading to the cliff. They formed a long V-shaped funnel, with the narrow end opening on the cliff. Except for the rocks, the women and children were unprotected. They had only their noisemakers, their robes to flap— and their raw courage, of which there was a plentiful supply.

Nranquar, the only man who had been completely hostile to Mark, led the warriors around in a wide circle. Mark felt the grass play out under his feet, and quite suddenly they were walking on ice. The footing was difficult, but the Danequa did not make a sound. It was darker now, just before the dawn, and there was no talking. Even Fang, struggling to walk on the ice, was completely quiet. He seemed to know, as did Mark, that if he made a sound Nranquar would destroy him without an instant's hesitation.

Nranquar had taken them neatly into position now. They were behind the mammoth herd, between the huge animals and the open ice sheet. The men of the Danequa arranged themselves in a broad semicircle behind the quaro, waiting silently in the darkness. Mark, Tlaxcan, and old Roqan, who, although somewhat lame, had insisted on staying with the warriors, built up a pile of kindling wood on the ice. The wood had been carried with them, and it was arranged in a curious fashion. First there were wood shavings, to serve as paper. Then smaller sticks were added, and after them larger ones. The largest wood used in the actual fire consisted of sticks not over an inch in diameter, and wide air spaces were left between them. It was essential that the fire catch in a hurry when it was lighted, for the failure of the fire would mean disaster. Placed carefully end to end around the fire, with only their tips in the flame area, were dried and treated torches, one for each warrior.

The eastern sky began to glow softly with the approach of the sun, and the gray light of dawn filtered across the cold ice sheet. Mark strained his eyes, but could not yet see anything. He heard restless coughs from the invisible monsters, and twice an ear-splitting trumpeting, startlingly near, cut through the chill air. Mark swallowed hard as the familiar dryness of excitement choked up his throat, and he felt his heart thumping so loudly in his chest that he was almost afraid the sound would carry to the quaro herd and alarm them.

The light increased, and Mark could make out several of the nearer warriors, crouching in their positions on the ice. He looked out ahead, across the flatly gleaming ice. He was sure that he saw something out there now—great blotches of blackness, enormous shadows that moved and swayed as he watched.

The sun crept higher; its rim inching almost over the horizon. Mark felt his hands sweating and he wiped them on his furs.

"Now, Mark," old Roqan whispered sternly, "light the fire quickly, and see that you do it right."

Mark dropped to one knee, the matches ready in his hand. Tlaxcan stood by with his fire drill, just in case the magic failed to work, as magic sometimes did at crucial moments. Mark struck the match, cupped it carefully, and fired the wood shavings. A tiny trickle of flame crawled along the shavings with agonizing slowness, branched out, fired other shavings. Mark held his breath—and the fire caught with a puffing whoosh that exploded like a cannon shot in the silence.

Mark heard an excited trumpeting ahead of him, but he did not look up. He watched the fire, making certain that the torches were caught properly before he moved. Then he and Tlaxcan grabbed up the flaming torches and dashed at full speed down the line, Tlaxcan going one way and Mark the other, handing out the torches to the waiting Danequa warriors. It was the work of but a moment, and they ran back to join Roqan in the center of the line.

"Took you long enough," hissed Roqan. "In my day I could have done it in half the time. I don't know what's happening to this younger generation."

The sun touched the horizon—it climbed higher, Mark gasped and gripped his lance tightly. He could see the quaro now, and the blood turned to ice in his veins.

"Charge!" shouted old Roqan, before Mark had time to think.

Through the dawn, with the mists beginning to rise from the ice sheets, the Danequa moved to the attack. Mark charged with the rest, his torch gripped in one hand and his spear in the other, shouting and screaming at the top of his lungs, the barking Fang at his side.

There was no time for fear now, and Mark avoided looking directly at the trumpeting quaro. But a corner of his mind whispered to him as he raced across the ice through the rising mists—whispered to him that they were charging the titans of the ice, who would trample them to shreds if anything went wrong.

their flexible trunk being one of nature's experiments on the road that had finally led to man's opposable thumb and grasping hand. Beyond doubt, the mammoth was a worthy foe, and Mark wondered how many people would have cared to charge him with only a spear and a torch.

But charge the Danequa did, and Mark with them.

Mark yelled frantically, and waved his torch in fiery circles around his head. He knew that the success of the hunt depended entirely on keeping the mammoths confused by fire and noise; if they were allowed time to think clearly, they would squash the Danequa like so many buzzing insects hit by a baseball bat. The first step was to get them moving, and it was not an easy step.

It was the oldest military tactic in the book, surprise and panic. Like all tactics, it was wonderful if it worked. If it didn't . . .

The mammoths were in no hurry to move. They eyed the shouting warriors nervously, they trumpeted and shifted, their eyes began to gleam angrily, but they did not break. Mark screamed and brandished his torch, and one of the beasts backed away a little. But that was not enough. Nranquar suddenly dashed in behind one of the mammoths and jabbed him with a spear. The mammoth trumpeted angrily and spun around with surprising speed. He reared up on his huge hind legs, snorting. Nranquar stood his ground, yelling and waving his torch. It was a crucial moment, and Mark and Tlaxcan ran to help. If the mammoth decided to fight, he could probably handle all three of them without difficulty, and the other monsters would join in the massacre. The three warriors shouted, and Tlaxcan, with sudden insight, threw his torch like a spear at the rearing mammoth. The mammoth snorted at the heat, and came down with an earth-shattering impact. His tremendous feet missed the dodging men, but it was close. The mammoth eyed them warily, and then turned slowly away and lumbered into motion in the other direction.

Mark breathed easier, and was elated to see that the mammoth herd had joined the old bull and were jogging along toward the plains. Mark knew that they had not defeated the mammoths, in any sense. It was just that the mammoths, like most animals, did not want to fight at all. They wanted to be let alone, and doubtless considered the puny men as not worth killing. But they might change their minds at any moment; they had to be handled with skill.

As Tlaxcan had trained him to do, Mark joined in guiding the moving mass of the herd, flanking them and shouting to keep them on course. Fang learned fast, and dashed in to nip almost at the quota's heels, barking furiously all the while. Mark could not help thinking that he would have made a first-rate cattle dog. Fang was a big help, and Mark noticed that Tlaxcan was watching him approvingly.

Everything was going according to plan, with the morning sun smiling in the blue sky. Now they were running along the grassy plains, and Mark began to relax.

Instantly, he saw that he had let down his guard too soon.

There was no warning, no hint of a suggestion of any sort that it was going to happen. One minute, everything was moving smoothly; the next, tragedy struck with blinding speed. Three of the giant mammoths turned aside as one, and there was no stopping them. They simply walked over the warrior who confronted them, brushing aside his spear as though it had been a toothpick. The man was trampled into a pulp with frightening swiftness; in an instant, where once a man had stood, there was nothing. The three mammoths moved sedately off on their own affairs, and nothing could be done about it.

The warriors of the Danequa redoubled their efforts to hold the remaining twelve mammoths. There was really nothing to prevent the monsters from going with their fellows if they so chose—nothing but bravery and human voices and a few pitiful torches. But they did not go—they shambled with deceptive speed along toward the trap which awaited them.

Mark did not relax again. He shouted with all his strength, and when his torch was exhausted he threw it in the midst of the mammoths. Fang barked and snarled as if he really thought he could tear a mammoth to pieces if he felt like it. Tlaxcan maneuvered with mfinite skill and patience, a fighting smile on his proud face. Nranquar, whose bravery was beyond question, risked his life again and again to keep the trumpeting quaro in line.

Across the morning-wet plains they ran, and Mark felt his newly toughened muscles rise to the occasion and carry him forward without a tremor. He breathed easily, and his hand was steady. He had a healthy respect for the mighty mammoths, and he knew that they could wipe him out in a second, but he had also learned a healthy respect for his fighting comrades, the Danequa. They were not fools, and they would not have attempted the hunt unless they had thought they would be successful. The very fact that they were still alive was eloquent testimony to their skill in the past.

With the precision of trained experts, the Danequa warriors drew together into a compact group behind the mammoth herd at exactly the moment the beasts lumbered into the mouth of the trap funnel. The men shouted with renewed energy, and now the women and children sprang up on all sides, yelling madly, beating on drums, flapping robes in the air, and making a general racket with all sorts of noisemakers. It all made a terrific din, to which the mammoths themselves contributed by their trumpeting squeals and the vibrating thunder of their great feet.

For the first time, the nervous monsters began to get really excited. The noise kept them mentally off balance, and they were not thinking clearly. Their one impulse was to get away from the noisy, irritating creatures that seemed to swarm around them like angry bees. Not yet in a panic, but simply eager to escape, they followed the path of least resistance, which is usually the most dangerous road you can take, no matter what your destination. They lumbered skittishly down the line of howling humans, and as the sides of the funnel closed in, the noise increased. The mighty beasts lifted their powerful trunks and trumpeted angrily, and at last they broke into a run.

The earth shook beneath the heavy tread of the quaro herd, and the noise was deafening. Excited by their own running, the monster mammoths went faster, and faster still. They covered the ground at a surprising rate of speed, and the Danequa were hard-pressed to keep up with them. Their frantic trumpeting redoubled in strength, and Mark shouted with wild exultation.

The mammoth herd had stampeded.

Across the great plains, down the funnel of death, the great beasts charged, their yellowish-brown wool and long black hair tossing, their long trunks extended, their gleaming ivory tusks curving and shaking in the sunlight of early morning. Closer and closer to the yawning cliff thundered the quaro, and with every smashing step their speed increased. They were in a wild run, their one thought to escape from the noise and confusion all around them.

Too late, the lead mammoth saw the destruction which awaited him. He squealed horribly and tried to stop, his trunk waving frantically in the air as he sounded his warning to his fellows. But the time for thought was long past; the jaws of the trap had closed, and there was no mistake. Driven on by the bedlam behind them, and unable to see what lay ahead, the mammoths rushed down the rock-lined corridor of extinction. Their massed tons of bulk shoved then-struggling leader off the brink of the cliff, and he fell with a piteous bleat to the jagged rocks far below.

There was no stopping the racing monsters. Over they went, by ones and twos and threes, to fall crushed and broken to the foot of the cliff where the old warriors waited to finish them off. The morning air was split by their screams, and Mark had to grit his teeth to go on. Man, the killer, was killing again—and the innocent animals of the earth fell before him.

Mark could have saved his sympathy, however. There was one mammoth, at least, who had ideas of his own about who should be pitied. He was the last of the herd, he had seen his fellows die, and there was no mammoth behind him to push him over. Excited and confused as he was by the shouting bedlam all around him, he somehow stopped dead at the brink of the cliff. His red eyes glittered with hot fury, and he spun around to face his tormentors. He was at bay, and deadly dangerous.

They had to get him over—it was now or never. The warrior nearest to him did not hesitate, but rushed at the monster, shouting and waving his spear. This mammoth was not having any of that! He was smart, and he had learned his lesson thoroughly. He stood solid as a rock, unmoving, and his powerful trunk snaked out with the sudden deadly accuracy of a whip and coiled itself about the charging man. The warrior did not live long enough to scream. With a contemptuous flip of his trunk, the mammoth tossed his body over the cliff, there to fall among the animals he had killed.

There was a sudden hush among the Danequa. The mammoth poised himself triumphantly on the edge of the cliff, his trunk lashing out angrily. He stamped his huge foot and trumpeted loudly, his red eyes sweeping his enemies with hatred. For a long moment no man moved.

Then Nranquar walked proudly out of the group of warriors and advanced on the waiting mammoth. He was determined to force him back before more damage was done, and he had a still-burning torch in his hand. He held it before him like a shield, and his step did not falter. Ashamed by this display of raw

evidenced by a snort of rage and pain. But it did not stop him; on the contrary, it speeded him up.

The mammoth rushed at Nranquar who, defenseless, turned and ran. The man was not fast enough. The mammoth's deadly trunk whipped out with lightning precision and slashed sideways, knocking Nranquar down like a club. The warrior moaned once, and was still, though he was still breathing. The mammoth stopped, trumpeted angrily, and lifted one massive foot to finish the job.

Mark and Tlaxcan charged as one, shouting at the top of their lungs to distract the great beast from his task. The mammoth hesitated, his foot hanging in the air over the prostrate Nranquar, his eyes beadily watching the two rash animals who dared to charge him. Mark, somewhat lighter in build, outdistanced Tlaxcan by a few steps and raced right at the mammoth without pausing. He was actually between the long, curving tusks when the surprised monster backed up a step, freeing Nranquar, who struggled to get up but could not.

Mark knew that he was very close to death, but he was determined to show his friends, and most particularly Nranquar, the stuff he was made of. Death was no stranger to him now, and he faced it calmly.

The mammoth had moved back one step, but that was all. He was not going over that cliff, and that was that. He braced himself, bellowing. Mark, planted between the monster and the fallen Nranquar, so close to the mammoth that he could see the crooked red veins in his eyes, took a deep breath, aimed, and lunged with his spear, every ounce of his power and every pound of his weight behind the thrust. He felt the shock in his arms when the spear rammed home, and he heard the mad trumpeting of the bull mammoth. He could see the red blood staining the monster's woolly coat—and he caught a sudden glimpse of mighty ivory tusks tossing angrily, their sharp points digging at him furiously.

That was all that Mark remembered with any degree of clarity. A fiery pain stabbed through his side, and as he twisted away, something slammed into his skull with paralyzing force. He crumpled in front of the enraged mammoth, his face buried in the grass. Vaguely, as from an infinite distance, whispering down from the stars, he heard shouts and trumpetings as a battle to the death raged over his body. He heard Tlaxcan barking orders, and old Roqan telling everybody to stand aside and let a man in there. Something caught hold of his feet and he felt himself pulled along the grass, away from the fight. His brain began to spin, and whirled faster and faster, in many-colored circles and bubbles of light. His whole body seemed to be whirling, around and around, and now the colored light all flowed together and was shot through with darkness. Someone was running crazily through his brain, wearing a billowing cape of black velvet...

Blackness. Silence. His soul drifted on an infinite sea of calmness that had no waves and yet washed the shores of the universe. Mark knew that he was dead. It was good to be dead, with nothing to worry about ever again. He had often wondered what it would be like to die, and he had feared it. But now that it had happened it wasn't bad at all. Very pleasant, really, just drifting on forever . . .

"Mark."

Someone was calling him. Who could it be? He was all alone on the sea. "Mark!"

His uncle? What was he doing here, drifting with the dead? But no—his uncle was thousands of years away.

"Mark!"

Mark stirred. The vast, unmoving sea dissolved into nothingness. Plis head hurt. He opened his eyes and there was the sun and the blue sky. He saw a cloud. Mark moaned and decided that he was still alive. He wished that he were dead again.

"It's all right, Mark," said a voice. It wasn't his uncle, the voice did not speak English. "The quote-is dead, but you are alive. The great red flower will burn through the heavens many more times before you leave us. The evil spirits had you—they were dragging you away across the Sea of Shadows—but I have brought you back."

Mark's dazed eyes swam back into focus and he saw the owner of the voice. It was Qualxen, the shaman. He was smiling broadly, well pleased with his success in driving out the spirits with his magic. Mark managed a smile in return.

"You are the most powerful medicine man in all the world," Mark assured him, his voice weak with shock.

Qualxen positively beamed with delight. "Sleep now," the shaman whispered soothingly. "Sleep, sleep . . ."

Mark slept, and he did not dream. When he woke up again, it was dark. There was a robe over him, and his head was clear. He sat up, looking around.

He felt surprisingly good; the pain in his side had diminished to a throbbing ache, and a careful exploration with his fingers assured him that nothing was broken. His head was sore where it had been hit by the swinging tusk, but the soreness was all on the surface. He felt a warm glow of relief wash through him. He had evidently just been knocked out, and was not seriously hurt.

Mark got uncertainly to his feet, taking it easy at first, and at once a shadow detached itself from the others that filled the night and came to him.

"You are back with us," said a voice. "I have been watching you."

"Nranquar!" Mark said with surprise. "Is that you?"

"Yes, it is Nranquar. The others are down below the cliff, cutting up the meat."

"What happened? The mammoth . . ."

"Tlaxcan and Roqan drove him back—the whole tribe hit him at once. He died fighting, but no one else was injured."

There was an awkward silence then, and Mark became aware of the sounds drifting up from below the cliff—quiet laughter, the low voices of people at work, the chip-chip of stone tools. The world was curiously hushed after the bedlam of the hunt, and the silver moon was already high in a sea of stars, floating in lonely splendor through the night.

"Mark?"

"Yes?"

"I—I owe my life to you," Nranquar said haltingly. This man who faced death without a tremor was acutely embarrassed at showing his emotions, but he was trying. "I have stood in your way ever since you came among us, and now you have saved my life. My life is yours."

"It is forgotten," Mark assured him, placing his hand on Nranquar's shoulder. "I would be proud to call you my friend."

"You are one of the Danequa now," Nranquar said softly. "You are my brother."

Mark felt a thrill go through him at the words, a thrill and a tingling happiness. A few short months ago—or fifty-two thousand years ago, perhaps—these people had not even existed as far as he was concerned. They were savages, names in a book, dawn men who had once roamed the earth. And now their friendship and approval meant more to him than anything else in his life. He did not spoil the moment with words; all had been said that needed to be said, and he knew that now, whatever happened, the Danequa were his people, and he was one of them.

"Let us join the others," Nranquar said finally. "They are waiting for us."

Following Nranquar's lead, Mark felt his way down a path that led to the bottom of the cliff. The moon was bright and clear, but they did not need it when they reached the Danequa. Great fires were burning redly in the night, and the delicious smell of wood smoke filled the air, together with that of roasting meat. The Danequa were feasting while they worked, and they were tired but content. Mark noticed that they had recovered their dead, and the two warriors they had lost slept the final sleep under a robe by the fire. Their loss somewhat dampened the spirits of the Danequa, but there were no demonstrations of grief. There would be time enough for that when the work was done. Nor was this lack of feeling on then-part, Mark realized. It was just that these people lived with death at their side always; death was no novelty to them, and they had to save their sorrow for when they had time for it. Time enough to remember the dead after they were buried with their weapons and charms—time enough to remember the dead on the long winter nights, when the families were alone, when the spirits howled and moaned down the snow-driven winds.

Mark was greeted by soft smiles and cheerful waves that meant more to him than any enthusiastic demonstration could have possibly meant. He belonged now; he was not a hero, and did not want to be, but was simply one of the Danequa, sharing their joys and sorrows because they were his joys and sorrows.

Tlaxcan grinned. "You are just in time to miss all the work," he told him.

Old Roqan came up, wearing his perpetual frown, bringing a choice piece of meat and a chunk of split bone loaded with juicy marrow. "Here," he grunted, "since you are too late to work you might as well eat a little something." He gave Mark the meat and the marrow, the twinkle in his eyes taking all the sting out of his words. Mark gratefully dug into the tangy meat, and sampled the marrow, which was considered quite a delicacy by the Danequa. The marrow was the soft, red tissue that filled the bone cavities, and Mark found it rather salty but very good after he got used to it.

Roqal, the plump wife of Roqan, ran up, skipping and laughing, and told Mark that she thought he was just the bravest thing ever. He told her that she was beautiful, and she raced happily away to convey this surprising intelligence to her husband, who had different ideas.

When the Danequa had cut all the meat and hides that they could possibly carry on the return trip, they loaded it all on devices they used for transporting their belongings. These contraptions were quite simple, since the wheel was completely unknown to them, and they consisted of two long lean-to poles, which crossed at one end to form a V-shaped frame. The hides were fastened to this frame, and the meat was piled on the hides and tied in place. These were pulled with the open end of the V dragging behind, and were quite helpful. Mark had seen similar devices among the Indians, where they were called travois. He remembered that the Indians, in times past, had used dogs to pull small travois, and he tried to hook a small one up to Fang. Fang, however, whose knowledge of history was cheerfully less than Mark's, refused to cooperate, snapping at his improvised harness and looking at Mark with pleading eyes. Mark turned him loose.

"Guess it just doesn't pay to tamper with history, old boy," he said, scratching Fang's ears and giving him a chunk of meat. "You've done enough work for this day anyhow."

Fang wagged his bushy tail happily and nuzzled Mark's hand. Mark could not help thinking that here was a concrete example of a problem he had often wondered about. Could you change history, if you went back in time? The Danequa had not used any animals for transportation purposes, and his brief attempt to change that had failed. Had Mark changed anything, in any fundamental way, in his weeks with the men of the dawn? He doubted it, and doubted that he could even if he had worked at it. He was beginning to realize that there was more to changing history than just coming along with a new or original idea. A people and their culture had to be receptive to the idea. In his own time, politicians and others had found that out, although they expressed it in different words. They said that "the time had to be right" for change.

Leaving three warriors behind to guard the meat they could not carry, the Danequa moved out across the plains for home, their travois loaded with meats and hides from the hunt. Old Roqan walked in the lead, his slight limp hardly noticeable—and, indeed, he would have been furious if anyone had noticed it in his presence. Behind him walked Mark, Tlaxcan, and Nranquar, side by side.

The moon was full, a silver world of ice swimming through the star-flecked reaches of the universe. The pale moonlight bathed the procession in soft radiance, lighting their way across the plains. Mark felt strangely proud and humble, and something in the darkness of the shadows whispered to him that this night would live forever in his heart.

Behind him, a few scattered voices started a chanting song. Others took it up, their voices carrying eerily across the moon-drenched plains. Mark listened intently, trying to learn the song, not sure whether he should join in or not.

The song was not difficult, once Mark caught on to what the singers were doing. Not every line of the chant had meaning, he soon realized. The lines of the song were mixed in with lines of pure sound, sung

had briefly seen when he had first stepped out of the space-time machine. The beast looked like a giant rhinoceros, with a wicked horn on its snout, but he was covered by the same yellowish-brown wool Mark had seen on the mammoths. He was an unpleasant-looking customer, and Mark noticed that Tlaxcan gave him a wide berth. The woolly rhinoceros did not bother them; he was content with planting himself like a rock on the plain, his eyes stating quite plainly that he would be a good animal to leave alone.

All through the day Mark and Tlaxcan continued on their way, eating the dried meat mixed with berries and sealed by animal fat—called berry pemmican when used by the American Indians—when they were hungry. They were approaching the cliff from the southwest, and it was early evening before they sighted the rocky hills that surrounded the mammoth trap. Mark was surprised to see how easily he could make out the trail that had been left by the Danequa on their return trip to their valley home; the streaky tracks left by the heavily loaded, dragging poles in the grass were plainly visible to him. He was sure that he could have found his way to the cliff without help, and he was proud of the fact. He was learning, slowly but surely. But there was much to learn in this strange new world . . .

Nearing the cliff just as the sun was fading in the west, Tlaxcan shouted to warn his three friends that he was coming. His voice echoed hollowly through the hushed silence of the rocks, but there was no reply.

"Sleeping on the job, perhaps." Tlaxcan smiled. "It's lucky that Roqan is not here. He would skin them alive."

"It's not like them to sleep at a time like this," Mark said, a questioning note in his voice.

Tlaxcan looked at him. "No, it isn't," he said quietly, and Mark realized that he had feared that something was wrong from the first. It was hard to get used to Tlaxcan's habit of speaking lightly no matter what was on his mind. It did not pay to take him too literally, and Mark wondered idly how many men and animals had died, their last sight a glimpse of Tlaxcan, his smile calm and unruffled even with death in his hand . . .

"You there!" shouted Tlaxcan. "Where are you?" No answer.

"Is everything all right?" Silence.

"I don't like this," said Mark, loosening his .45 in its holster and taking a fresh grip on his lance. The cool evening breeze whipped across the plains, and its moan was the only sound in all the world. It was too still; the very air seemed to whisper danger. The two men moved forward cautiously, Tlaxcan slightly in the lead. Tlaxcan fitted an arrow to his sinew-backed bow, and unconsciously his body assumed a fighting crouch. He sniffed the air, his sensitive nostrils flaring wide.

As if guided by instinct, Tlaxcan changed his course a trifle so as to mount a near-by rise in the land. Clearly, he was uncertain about the wisdom of following the well-marked trail too closely until he found out exactly what was going on. They hurried up the hill, their light footfalls sounding unnaturally loud in the ominous quiet. Mark thought that he had never heard the land so still; there was not the rustle of an insect, not the chirp of a bird, nothing.

Sticking to cover without quite knowing why—for surely they had been spotted long ago if enemies were indeed about—they wormed their way up to a pile of jagged rocks and looked over. All was almost as they had last seen it in the little valley at the bottom of the cliff. The huge carcasses of the dead mammoths, chopped and carved as they had been by the Danequa hunters, still lay on the rocks, their remaining tusks gleaming whitely in the dying rays from the sun. The three guards left behind by the Danequa were still there too. But it was obvious enough why the three warriors had not answered their calls. The guards were as dead as the mammoths they guarded.

Mark looked down into the pit of death, Ins throat choked with horror. The hushed silence shrieked in his ears. There was something decidedly odd about the scene before them, something above and beyond the spectacle of their three friends lying dead and cold across the massive bodies of the quaro that they themselves had slain. For a long moment, Mark could not quite put his finger on what it was. Then he saw it.

"The vultures," he whispered to Tlaxcan, pointing into the gray air. "There are no vultures."

That was it. With the great hulks of the mammoths beginning to decay after a day in the sun, and with the three guards dead, the sky should have been alive with the ugly black vultures that fed on the dead. Moreover, there should have been carrion-eaters gnawing on the dead flesh—wolves, dogs, something. Fang's hackles bristled, and Mark's own neck felt a curious, nervous tingling. If there were no men around, there;

a terrible, dreamlike impression that the interlude with the Danequa had been but an unreal fantasy, that he had always been running with the fearful Neanderthals behind him, eternally, forever, for the rest of his life.

For the rest of his life. That might not be very long.

But the paralyzing fear abated slightly, and he saw that the half-men were not gaining on them. Actually, it was easier this time than it had been before. He was in far better condition, he was not alone, and the world was no longer so strange to him as it had once been. But all that would be scant comfort if that snarling pack of man-things ever caught up with them, and catch them they would, eventually, unless Tlax-can knew his stuff.

Tlaxcan had no breath to waste in talking. However, sensing his friend's thoughts, he managed a quick smile of reassurance that picked Mark up amazingly. Mark knew that if anyone could get them through, it was Tlaxcan. That, of course, was the question—could anyone?

Mark stopped thinking. He realized that Tlaxcan knew the country better than he could ever know it, and his job was simply to follow his lead. Mark was intelligent enough to recognize a real leader when he saw one, and he did not foolishly try to exert his own influence in a situation he was not equipped to deal with. And he did not want to think about the snarling half-men behind him; above all things he must not permit his muscles to become constricted with fear. In New Mexico, he had once seen a bird frozen with fear at the sight of a snake slithering toward it. All the bird had to do was to fly away, but it simply could not move. It stood rooted to the spot, staring, until it no longer had eyes with which to see.

Mark tried to imagine that this was just a race he was running, a cross-country marathon. He kept his eyes on Tlaxcan's broad back and matched him step for step. He was dimly aware that night had fallen, and he was seeing by starlight. He felt the grass under his feet turn to rock as they raced into the mountains, and he was conscious that the grunting snarls of the Neanderthals were fading behind him.

Finally, there was only the pounding of their own feet, the dry gasping of their own breathing. They were alone—they had shaken them! Tlaxcan stopped, and Mark sat down to catch his wind. Tlaxcan instantly pulled him to his feet.

"Do not be a fool, my friend," he panted. "One does not escape from the Mroxor so simply. The night has confused them for a moment, that is all."

Mark shook his head, ashamed of his own stupidity. "That is what happens when you turn off your mind," he apologized. "What do we do now?"

"We build a fire," Tlaxcan answered surprisingly, "and we do it fast."

Mark looked at his friend in amazement, but there was no time to discuss strategy. If Tlaxcan said to build a fire, then that was what they were going to do. Mark pitched in with frantic speed, gathering some dead and rotten pine. He split the shavings with his knife, and he and Tlaxcan piled kindling and boughs together in record time. Mark knelt with his precious matches, and eyed Tlaxcan questioningly.

"They will see the fire," he said logically. "They will find us and come here."

Tlaxcan smiled. "They will find us anyway," he explained. "They will come, but we will not be here."

Wondering, Mark lit the fire. It blazed up brilliantly, and Mark reflected that he was getting to be an expert at building fires. If he ever got home, he knew that he would never again waste more than one match in starting a fire.

"Now," said Tlaxcan hurriedly, "we need torch branches—all we can carry. Be quick, we have little time."

The two men searched through the night and managed to locate six dead branches that would serve as torches. They lit just one of them, which Tlaxcan carried, and then they left the fire and climbed on into the hills. In a short time they came to a dark cave, which had evidently been Tlaxcan's destination, and they were not a moment too soon. A chorus of snarling shouts below them told them that the half-men were already at the fire.

The cave mouth was dark and unwholesome-looking. Damp, faintly foul air rose out of its depths and Mark felt an unreasonable shudder pass through him. Caves, like houses, had personalities of their own. Some were warm and cozy, good places to sleep in. Others were vastly mysterious and hinted of scenic marvels underground. And still others were dank and evil-smelling, with a nameless dread dwelling in their subterranean caverns, crawling with wormy horrors that had never known the light of day.

It was not an inviting place to enter. Mark quickly saw, however, the wisdom of Tlaxcan's move. They could not elude the Neanderthals for long, even in the mountains; it would not do to count on another streak

he could, the light from Tlaxcan's torch, as it wound on down into the cave. He knew, of course, that where Tlaxcan had gone he could also go, but it was weirdly uncomfortable to have to put his feet down on rocks that he could not see, feeling all the while that he might just go on forever, down, down, down . . .

The dank, unpleasant smell increased as they pushed on through the caverns. Mark could not quite decide what it was about the smell that was so oppressive; it was a nameless thing, all the more chilling because he could not positively identify it. It was not merely a dead smell, although the cave had the stench of death about it somehow. Nor was it only the dampness, or the stifling closeness that one often knows deep in the earth, with the untold tons of rock pushing down on you from the clean world above.

It reminded Mark of a sewer pipe he had once crawled into as a child. The pipe had stopped abruptly and turned into a stone tunnel, where the sewer line ran under a railroad track. He had groped forward in the darkness, the batteries in his small flashlight beginning to give out. He splashed excitedly through the murky ooze, still on his hands and knees, putting one hand ahead of the other to feel his way along. First his right hand, then his left hand, then his right hand, then his left hand touched something. It was cold, cold and slippery. Horrified, he could not take his hand away. The thing was round and soft and flexible. Mark ran his hand along it, shocked almost out of his senses. It was long. His other hand shaking so that he could hardly hold the flashlight, he turned the fading beam downward. There on the rocks, dead glazed eyes staring at him, was a six-foot rattlesnake that had been dead too long . ..

That was the way this cave felt,

Down and down Tlaxcan went, not even bothering to look behind him. Mark could not hear the half-men now. Had they given up? Were they squatting around the cave mouth, waiting? Or were they stalking them in silence through the Stygian blackness, their red eyes fixed on Tlaxcan's dwindling torch even as Mark's were?

Fang whined loudly and then subsided into silence as Mark patted him with a reassurance he did not feel. Mark tried to tell himself that he just had the willies, that the worst was over, that Tlaxcan clearly knew what he was doing and where he was going. That helped some, but the eerie feeling persisted. Mark kept seeing that dead snake, soft and horrible under his hand.

Tlaxcan fired up another torch from the dying flames of the first one and hurled the first one away. It sizzled and hissed as it fell into a shallow basin of oily water, and then winked out. The new torch chased the shadows back momentarily, and Mark caught a sudden glimpse of fantastic rock formations all around him in a somber and brooding series of archways and branching tunnels, rearing stalagmites and hanging stalactites. It was weirdly beautiful, and yet infinitely dead. It looked like the cold surface of the moon.

On and on they went, with Tlaxcan as sure-footed as though he were trotting through an open field for exercise. He twisted and turned, following a trail that Mark could not see. The damp heaviness in the air increased, almost as if all the weight above them were pushing down on it with physical force. Far in the distance,

Mark could hear what sounded like the gurgle of running water. That was all. There was no sound to alarm him, and he noticed nothing that was the least suspicious. And yet the feeling of dread stayed with him, seeming to seep through the very air itself.

The Neanderthals were gone as though they had never existed, and Mark did not believe that they could have followed them all this way without once betraying themselves. Either they had gone back to the dead mammoths, or else they were waiting for them at the mouth of the cave. Neither Mark nor Tlaxcan was in any hurry to go back and find out for sure, so they kept on going down into the depths of the cave. Undoubtedly, Mark figured, Tlaxcan knew of another exit to these caverns than the one by which they had entered. Otherwise, they were trapped more certainly than they had ever been outside, and Tlaxcan was not dull-witted in any respect. If the Neanderthals knew of that other exit, too, however . . .

Fang kept drawing back, afraid to go on, and then hurrying madly to catch up, afraid to be left behind. What was the matter with him? Mark knew that the wolf-dog was used to caves, and he had proved his courage many times over on the mammoth hunt. He didn't scare easily, and if he was scared at all, there was a reason for it. Such thoughts did little good, however. They could not possibly go back now, even if they knew for sure that danger lurked in the black depths of the cave. They could only go forward, down into the earth.

"Not much farther down now," Tlaxcan said suddenly, the unexpected sound of his voice startling in the hush of the cave.

"Let's hope not," Mark answered, keeping his voice cheerful. "It should start getting hot any minute now."

Tlaxcan, of course, did not catch Mark's reference, but he did not question him. "We have lost the Mroxor," he said instead.

"Are you sure?" Mark asked.

"The Mroxor will not follow us here," Tlaxcan assured him.

"Why not, Tlaxcan?"

"This cave is not a good cave," Tlaxcan said quietly, summing up all Mark's vague thoughts in a single sentence. "We are very far from the sun."

The second torch burned down to a mere twig with a vanishing flame, and Tlaxcan hurriedly lit his last dead branch. Mark was grateful for the light, as was Fang, who wagged his tail in relief. Light very decidedly made a difference, and Mark did not even like to think about being lost in this underground maze in total darkness. He still had three branches of his own, but he realized that that was none too many. The dead wood burned fast, and not even Tlaxcan could find his way to the surface again without a torch. There must be fresh air moving through the cave, Mark thought, since the torch seemed to be blowing very slightly. It could not be much, since he could not feel it at all, but its presence was encouraging.

Abruptly, the cave floor leveled out underfoot. The steady downward grade vanished, and Mark had been walking so long on a slanting surface that for a moment it was difficult to adjust his stride to more normal conditions. He had a distinct impression of open spaces all around, as opposed to the pressing sensations that sensitive individuals always felt in narrow caves. In the uncertain light of Tlaxcan's torch, he could not even see the walls of the cave, and the roof was lost in the shadows above his head. The gurgle of water was quite close now, and it echoed with surprising loudness against the distant rocks. They were evidently in a huge underground room of some sort, far beneath the surface of the earth.

Tlaxcan did not break his stride, and Mark had to hurry to keep up with him. But the strange, oppressive smell was even stronger in the vast chamber, and Mark found that it took quite an effort of will to keep from looking back over his shoulder. The smell, he was now able to determine, was not one smell but several, all mixed up together. One of the smells, unless he was very much mistaken, was that of dead fish. At first thought, this seemed strange, but then he remembered the fish caught in Mammoth Cave in his own day and age. There was a stream here, and therefore there could be fish. The other smells he could not yet identify, but there was one question that needed answering in a hurry.

Who, or what, caught the fish down here?

No one answered his unspoken question, but obviously Tlaxcan had also been doing some figuring with regard to those dead fish. He quickened his pace, torch held high aloft, and swung his bow around in his free hand so that it was ready for action. Fang caught the heightened odor too, and whined and growled by turns.

They crossed an icy stream, and Mark felt as though he were stepping barefooted through piles of drifting jellyfish. He did not relish the thought of wading through water that he could not see, and he was tense and nervous, waiting for something to happen. Nothing did, however, and they went on through the great cavern without incident.

Tlaxcan led him into a small branching tunnel that shortly opened up again into another cave room, this time much smaller than the one they had just been through, but still a cavern of considerable size. It was pitch dark, and Tlaxcan's torch was growing dim. Fang whined constantly, and almost crawled along, fiat on the floor. Mark felt the hair on the back of his neck stand up, and he began to shiver uncontrollably. Even Tlaxcan slowed his pace, his breathing harsh and shallow in the stillness.

Something was wrong with the room.

Mark could not for the life of him figure out what was the matter. The smell was stronger, but that was all. There was no sound, save for Fang's whining and the chuckle of water from the cavern behind them. All was darkness, darkness and silence, and yet . . . Eyes.

There were two eyes looking at them from the blackness of the cavern. Two eyes where no eyes could be, glowing with yellow flames in the gloom under the earth. There was not a sound, only the two unblinking eyes like misplaced stars watching them. The eyes were bad enough, but their position was worse.

The eyes were a good fifteen feet off the ground.

"Tlaxcan," Mark whispered. "Tlaxcan—"

With the awful suddenness of a thunderclap when there is not a cloud in the sky, an ear-splitting roar bellowed through the cave. The sound blasted against Mark's ears, numbing his brain with fear. It was the most fearful sound he had ever heard in his life—and coming as it did from fifteen feet off the ground . . .

"Get back, Mark!" shouted Tlaxcan. "Back in that corner!"

Mark did not move. Frightened as he was, he had not the remotest intention of leaving Tlaxcan to fight a rear guard delaying action by himself. Instead, he moved up beside him. Forcing his nerves to steady down, he took one of his torches and lit it from the dying flame of Tlaxcan's. The light flared out suddenly, and he caught a quick glimpse of something enormous and black under the eyes. The thing roared again.

It started forward.

Tlaxcan threw his feeble torch with all his strength at the padding figure of darkness, and the thing snarled hideously, its yellow eyes gleaming. It hesitated, brushing the flame aside.

"Now," hissed Mark. "Back together."

To have only one direction from which to defend themselves, they backed rapidly into a corner, with Mark holding the torch high in the gloomy air. Fang growled deep in his throat, no longer afraid now that the danger was real. He knew that he did not have a chance against the monster before him, but he was determined to die fighting.

The thing roared again, its voice wet and ugly.

"Whatever we're going to do, we'll have to do it quick," Tlaxcan said evenly. "We need these torches to get out of here."

They had their backs to the wall, with no room to maneuver. Their supply of light was going up in smoke. When the light gave out, and left them alone in the darkness with that monster—Mark tried not to think about it.

They would have to act, and act now. But that thing

reputation of having strong medicine, and he knew too that his chances against the thing in the cave with a bow and arrow were slim almost to the vanishing point.

"You hold the light," Mark said, thrusting the torch into his hand. "I will try my magic."

Tlaxcan held the torch aloft, and with his other hand he gripped his bow. Magic was all very well, he knew from experience, but it had a tendency to be un-dependable. Sometimes it worked, sometimes it did not. It never hurt to have something in reserve.

Mark himself was far from feeling as confident as he sounded. To be sure, his .45 with its three bullets was a more effective weapon than a bow and arrow could be, even when the more primitive weapon was handled by such an expert as Tlaxcan. But a pistol, for all his talk about magic, could not perform miracles. A .45 packed a formidable wallop, but it was not accurate even at close range. What he needed was a high-powered rifle with rapid-fire action, and even then he would not have felt completely secure. He was under no illusions that one shot from the .45 would knock the monster over like a rabbit. That thing had bulk, and he felt oddly like someone trying to stop a tank with an air rifle. The thing roared again, deafeningly. It started forward.

It was now or never. Mark's nerves were steady, and he managed to think of the nightmare creature simply as a target. He ignored the roaring sound and aimed carefully at the thing's yellow eye. He tried to breathe evenly, and he remembered to squeeze the trigger gently, so as not to throw the weapon off its aim. He could feel cold sweat dripping down his body.

Mark fired. The .45 went off with a slamming blast in the still air of the cave, and Mark had a wild fear that the vibrations from the shot might start a landslide, sealing them in forever or burying them under tons of rock. The gun kicked back against his hand, and one yellow eye winked out.

A terrible roar of pain filled the cave and Mark knew that his shot had struck home. But the thing was not dead; all Mark could see now was one yellow eye and the vast bulk of darkness beneath it. The monster screamed in agony, and launched itself at them like an avalanche.

Mark did not fire wildly. He aimed for the other eye and squeezed the trigger again. The shot boomed out when Mark could already feel the thing's fetid breath upon him, smell the underground monster's terrible nearness. Dimly, he was aware of Tlaxcan dropping the torch and loosing an arrow into the black bulk. Fang growled deep in his throat and charged to meet the attack.

But it was not enough. The warm and stinking mass of the monster kept coming, and before Mark had time to fire his last shot it was upon him. He thrust out his hands futilely and was thrown back against the cave wall, dropping his gun in spite of himself. He closed his eyes, waiting for the crush of unseen jaws, feeling the terrific weight of the thing against him.

Nothing happened.

Mark opened his eyes. Desperately, he crawled out from under the dark mass, feeling something wet and sticky on his hands. "Tlaxcan," he gasped. "What—"

"It is dead," Tlaxcan said quietly, a deep respect in his voice. "You have killed him with your magic."

Reaction set in and Mark was suddenly and thoroughly sick. Then he felt better. He came back and looked down at the dead monster that had waited for them in the depths of the earth. Fang was wagging his busy tail furiously and rubbing against Mark with a grateful affection that knew no bounds.

"What was it?" Mark asked, picking up his fallen .45 and returning it to its holster.

Tlaxcan picked up his torch and held it so that Mark could see the dead body. Even in death, the thing was formidable. Its eyes were gone, vanished in bloody spots where the .45 slugs had done their work. An arrow was buried in its shoulder. It was over fifteen feet in length as it sprawled on the cave floor, lying in a growing pool of its own blood. It was covered with long, shaggy black hair, matted with filth. It had only a suggestion of a tail, and its long snout was open in a death-grin of defiance, its yellow fangs gleaming in the torchlight.

"It is Groxur," Tlaxcan said. "The Dweller under the earth."

This name, for all its colorful suggestiveness, did not tell Mark what he wanted to know. He examined the thing as carefully as he could in the flickering light, but he knew that time was running out on them and they had to hurry if they were to make it out of the cave before their torches expired. The last one was already dying, and Tlaxcan lit another. That left them with just one spare.

There was no time for curiosity. With Tlaxcan taking the lead and setting a rapid pace, they left the chamber of death and proceeded on through the branching tunnel Mark's thoughts were still filled with the sight of the monster they were leaving behind, and the only animal with which he was familiar that he could liken the thing to was an enormous bear. That made sense,, he realized, since the thing evidently lived mostly on fish, at least while it was in the cave, and he remembered hearing stories about the huge cave bears that had formerly lived beneath the earth. He shuddered a little, knowing that never again would he see a bear without visualizing that horror in the cavern under the world.

On and on they went. When their torch finally expired, they lit their last one and hurried on, almost running now. Over and over again, one thought kept churning through Mark's brain: he had only one bullet left in his .45, and no prospects for getting any more. If he was ever to get back to the space-time machine, he would have to do it soon. The .45 had twice saved his life, and he had a hunch that without it he could not expect to live long in the savage dawn-world in which he found himself. But how could he possibly return to the space-time machine? There was only one* chance . . .

It was morning when Mark and Tlaxcan, with the happily barking Fang, emerged from the dank cave into the clean air and sunlight of a new day. Tlaxcan's strategy of coming out by way of another exit proved successful, the half-men were nowhere to be seen. They threw away the smoking remnants of their last torch and worked their way down out of the hills to the plains below. There was no sign of danger, and they struck out for the valley of the Danequa with their spirits once more free and high under the rising sun. The news they carried, of the massacre of the

Mists of Dawn

three Danequa guards by the Neanderthals, could not dampen their spirits too much. They were too glad just to be alive themselves.

Their underground maneuvering had carried them back toward the valley home of the Danequa, and their trip across the plains proved uneventful. They walked all day, pausing only to cook and eat a deer that Tlaxcan brought down with a well-placed arrow, and they pushed onward through most of the night. They arrived in the valley of the Danequa early the next morning, just as the Danequa were rising for another day. The tumbling cascades of the sparkling waterfall, the wonderful green of the grass, the smell of the clean pine trees—all of it was more beautiful and delightful than it had ever been before. The two men drank it in with their eyes, and listened to the happy shouts of the Danequa with new-found warmth in their tired hearts.

It was good to be home.

Mark and Tlaxcan reported the details of what they had seen to the warriors of the Danequa, greeted their friends, and then both hurried on up to Tlaxcan's cave. Tlaxcal shooed little Tlax away, and the two men were asleep in an instant as outraged nature took its toll. Fang trotted obediently off to what he doubtless considered his own cave and promptly went to sleep himself.

When Mark and Tlaxcan awoke, night had come again. The cold wind whispered through the valley grasses and sighed through the branches of the lonely pines, and the stars sprinkled the heavens with clusters of frosted diamonds. In the distance, they could hear the pleasant muted roar of the great waterfall, now a familiar backdrop against which they enacted the drama of their lives. And they could hear something else as well. Drums.

Mark and Tlaxcan got up, feeling much refreshed, and walked across the valley floor to where they saw the leaping flames of the Danequa fires and heard the rhythmic throbbing of the brooding drums. The cold wind was fresh in their faces and the tall grasses brushed softly against their legs as they walked.

"Those are the council drums," Tlaxcan said quietly. "My people are holding a council of war."

Mark raised his eyebrows. "The Mroxor?" he asked.

Tlaxcan nodded. "They have dared too much," he said. "They have killed our warriors and they have stolen the quaro which we fought to bring down. This cannot go on. We have fought them before, and now we must fight them again."

A great shout went up when the Danequa caught sight of Mark and Tlaxcan, and they were escorted to the center of a circle of council members. There Tlaxcan repeated the story of what they had seen, and told of how Mark had destroyed the Dweller under the earth with his magic. The story lost nothing in the telling, and Mark could sense the murmur of respect which ran around the seated figures about the council fires. Qualxen, the shaman, all painted up and looking very impressive for the occasion, eyed Mark with a rather worried look on his face. Mark was getting altogether too powerful, and if it came to a contest of supernatural skills Qualxen feared that he might be out of a job. Mark smiled at him in a reassuring way, however, and the shaman relaxed visibly.

One by one, the elders of the Danequa were called upon to give their views on the Mroxor raid and what should be done about it. There was a great deal of talking, most of it ceremonial in nature, and it went on far into the night. Mark noticed the thin, pale figure of Tloron, whom he had not seen since he had first come among the Danequa, sitting alone by one of the fires. Tloron was silent, as he always was, and seemed to be looking into the flames. What did he see there, dancing in the night? Mark knew that Tloron was a holy person to the Danequa, but he realized that, oddly enough, he knew no more about the man now than he had known the first time he had met him. What was he like, that lonely figure? What did he think in those silent thoughts he never shared with anyone?

The general view seemed to be that the Danequa should organize a return raid upon the Mroxor, in order to punish them for their actions against the Danequa. In fact, such an overwhelming majority of the speakers favored this move that Mark was for some time at a loss to discover why the council went on so far into the night. Part of the reason was undoubtedly the fact that the meeting was ceremonial in nature. There were set things to say, set procedures to go through, all of which were time-consuming. And the Danequa were in no particular hurry, inasmuch as •such diabolical inventions as watches had not yet made their appearance in the world. If they finished in time, they could attend to it tomorrow. If not, the day after that would be fine. If they had to postpone it a week, or a month, or a year, what real difference did it make? One time was quite as good as another,

But that was not the whole reason. There was a decided earnestness about the proceedings that could not be entirely explained in terms of ceremonialism. The council of the Danequa was clearly doing its level best to reach a decision, and as far as Mark could see, every single member but one was in favor of the same plan!

The one opposing speaker, a middle-aged warrior named Dranqan, maintained that they had already lost more men than" they could afford. It seemed to Mark he was not unreasonable in his position. It was his view that the time was coming for the Danequa to break camp for the winter and go their separate ways after the herds. They should not waste warriors in a fight with the Mroxor, which would after all not benefit them in any way. Dranqan, in a sense, was the voice of reason. He was not swept away by proud feelings of revenge, but rather was taking the long-term view of things. Mark suspected that Dranqan might be around for many years after the others were dead and gone.

Around and around the council fire the debate went, each member in turn repeating the same arguments that he had used before. But Dranqan would not move from his position, and it became clear to Mark that the social organization of the Danequa was in some ways an ultimate democracy; it was not enough to have a clear majority, but rather every decision had to be unanimous. This system had its drawbacks, to be sure, and one of them was readily apparent to Mark. What happened if one member held out indefinitely? Would the meeting go on forever, with nothing ever accomplished?

appreciate what one has. A person never fully understands the gift of life until he has stared death in the face and felt nothingness closing in all around him. Similarly, Mark looked at his surroundings with new eyes, noting every detail of the cascading waterfall, the hills honeycombed with dry caves, the dark pines with their sweet-smelling needles, and the long green grasses that rippled like a velvet sea under the blue sky and the great red flower that was the sun. These were things that he wanted to keep a part of him always.

Mark spent much of the time just wandering around the valley with Fang, talking to the friends he had made in the lost shadows of man's history. Roqan was storming around telling everybody about the way they would have done it when he was a young man, while his wife, Roqal, only slightly happy with the intoxicating kiwow, was working on his weapons. Roqan could not quite bring himself to compliment Mark directly upon his exploit in killing the Dweller under the earth, but he did hint that if Mark kept up the good work he might one day be as good a man as Roqan. As usual, the twinkle in old Roqan's eyes clearly contradicted the gruffness of his words. He even forced a cherished stone knife on Mark as a gift, although he was careful to make it seem that he was almost insulting Mark to offer it to him.

With Nranquar, now a fast friend, he spent many long hours watching the clean water plunge over the waterfall into the sparkling pool below. He talked across a flickering fire to the shy Tlaxcal, the wife of Tlaxcan, and finally gave her his steel pocketknife to help her in her work. Little Tlax, who by now was treating Mark as one of the family, was currently engaged in trying to dig a cave of his own in solid rock with a blunt stick he had picked up somewhere. He made very little progress, but he beamed contentedly most of the time, and Mark would have been proud to have him for his own son.

Mark and Qualxen, the shaman, held many long and involved discussions about the intricate tricks of the magic business. Qualxen now regarded Mark as just about the most powerful medicine man he had ever heard anything about, and he was quite proud to be seen in his company since it increased his own stature among the Danequa. Mark treated the man with good-natured tolerance, priding himself upon his superior knowledge, until the shaman looked at him one day and smiled.

"Since you are leaving soon to return to the land of your fathers," Qualxen said quietly, "you should get to know Tloron before you go. He is a very holy man."

Mark stared at the shaman. "Leaving?" he said. "I have told you nothing about leaving."

"You are going," Qualxen repeated. "You will not return."

Mark looked at Qualxen. The shaman smiled cryptically at him, but said nothing further. A good guess, Mark told himself. Pure and simple coincidence. Nonetheless, his respect for Qualxen jumped considerably. He had told his plans to no one—how could the shaman have known?

Rationally, of course, Mark knew that it was all a question of good timing and luck. But, emotionally, he sometimes wondered. With every succeeding age, the knowledge of the preceding one had been shown to be worthless superstition—or so some people would like to have you believe. The age of the twentieth century, too, would pass on and become obsolete under the merciless tread of time. What would the people of the future think about the proud knowledge of 1953? How much did man really know, and how much did he just think he knew?

All questions of supernatural powers aside, however, Mark was curious to know more about the silent Tloron. He sought out Tlaxcan and asked him where Tloron was. Tlaxcan told him he was at work in a cave far beneath the earth, at work in the sacred chamber of the Danequa. Tlaxcan did not actually say the word "sacred" of course—what he said was that the cavern was strong with power, force, mana; that it was heavy with the spirits of the earth, of the sub-earth, and of the sky. But his feelings toward the place were closely akin to the concepts of sacredness, and so it was thus that Mark translated Tlaxcan's words to himself.

Tlaxcan offered to take Mark down to see Tloron at work, and Mark readily agreed. They took torches and entered a large cave that was vaguely familiar to Mark, although he was certain that he had never been in it before that he could remember. They walked along through the dark tunnels until Mark judged that they were a good two miles beneath the earth, and still Mark was haunted by a feeling that he had been through the cave before. He seemed to remember as from a vast distance each turn and twist that the tunnel took. Where had he seen it before? When?

After an hour's walk, they noticed a light glowing ahead of them in the cave. They rounded a corner and stopped, not saying a word, looking at the scene before them.

In this deep recess of the limestone caverns, far beneath the surface of the earth, the pitch-black gloom was illuminated by two stone lamps set in the rock walls. The lamps were filled with animal fat and their wicks were soaked twists of moss. In the soft light of the stone lamps, the pale Tloron worked alone, painting with crude clays and berry dyes and charred sticks upon the side of the cave. He worked very slowly, unsurely, feeling his way. He stopped often to survey his work with a critical eye.

Mark stood very still, hardly breathing. He could not express the emotions that raged within him at that moment. He felt much as an eavesdropper from the future might have felt in looking over Shakespeare's shoulders when he was writing the great soliloquy in Hamlet. Mark knew that he was having the unique experience of seeing one of the wonders of the world in the moment of its creation.

What was the silent Tloron painting? For the most part, he was working with animal figures. There was a wonderful bison, muscles rippling. There was a mighty stag, antlers tossing proudly. There was a stately mammoth, his long trunk curving back along his side. The animals were drawn in profile, without perspective, and they were vivid with black, brown, red, yellow, and white coloring. In the soft light of the soapstone lamps, the painting was startling in its force and clarity.

Startling? That was hardly the word for it, for Mark had seen the painting before. He had seen it almost fifty-two thousand years in the future.

When he had visited France with his uncle, he had been in this same cave, seen this same painting, the colors faded by the drift of years, but still remarkably well-preserved. This painting now before his eyes was the first great art in all the history of mankind; it was the oldest of the masterpieces of man. Mark had seen the painting in 1949, when he was thirteen years old. Now he was seeing it painted before his very eyes when he was seventeen years old, and almost fifty-two thousand years younger in time!

What could he say to this silent man, who worked all alone under the earth, fumbling, unsure, reaching out through the darkness for the beauty that he saw within him? How could he tell Tloron that the work he was laboring over would be cherished by all men for a longer period than any other art that would ever be created by man until the end of time?

He could not say anything. He nudged Tlaxcan, and, picking up a small dish of red pigment that Tloron had discarded, he started back the way he had come. He knew that Tloron did not wish to be disturbed, nor did he wish to chatter his time away. Tloron was doing something great, and Mark had no ill-bred tourist wish to interfere or hinder him in any way.

"Tloron is a very holy man," Tlaxcan said, pleased that Mark had not disturbed him. "He makes the game plentiful and the hunting good."

Mark nodded, remembering some of the things that Doctor Nye had told him about magic on their tramps through the mountains of New Mexico. There were two basic types of magic, black and white—the black used for evil, and the white for good. Whether the magic was black or white for you depended, of course, on which side you happened to be at the time. Among the types of white magic, ritual magic to insure the success of the hunt held a high place. The idea was that you painted an animal on the cave wall, and just as it appeared there so it would appear in the fields, ready for the kill. So it was that the first great art in human history was in part magic—as, in a sense, all great art has been ever since.

Toward the entrance to the cave, but still well-protected and far underground, Mark stopped and asked Tlaxcan to hold the torch for him. Tlaxcan smilingly obliged, and Mark took a flat stone about a foot and a half in diameter and began to draw on it.

"A little magic of my own," he explained to Tlaxcan, who did not laugh at him. He had seen the results of Mark's magic before.

With the pointed end of a rock, Mark carefully sketched a jet aircraft in red dye. He took his time, and made it accurate enough so that its identity was unmistakable. Underneath that, he slowly lettered a famous equation: E = MC². This was the formula worked out by Albert Einstein, to the effect that energy equaled mass multiplied by the square of the speed of light, an idea that was instrumental in the development of atomic energy.

When he had finished, Mark took the rock and very carefully placed it behind a large boulder high on a ledge in an out-of-the-way corner of the cave. He smiled to himself when he had finished, knowing that he now had proof of a sort, in case he should ever need any, that he had actually been back in space-time to the land of the Danequa. He started on toward the entrance of the cave with Tlaxcan. He could tell them about that stone, and he could take them to it, and there it would be, fifty-two thousand years old with a drawing of a jet plane and one of Einstein's equations on it. Of course, everyone would claim that it was a fake—but then you never could prove anything to people who had decided in advance not to believe your evidence.

What would happen, he wondered, if some anthropologist or archaeologist dug up that stone before he got back to it? He knew for certain that it hadn't been discovered before he left in the space-time machine in 1953, but what about after that if he never got back? He could well imagine the absolute dumfounded confusion of the man who found that stone associated with Cro-Magnon culture! Even with his layman's knowledge of the profession, Mark strongly suspected that the hypothetical anthropologist would promptly bury the stone again and forget about it, rather than attempt to prove that his find was a genuine one and that someone had evidently known about Einstein and jet airplanes during the Ice Age.

As they walked back out of the limestone caverns into the open air and saw the preparations for the war party all around them, Mark was strongly tempted to try to tell Tlaxcan something about himself and where he had come from. He gave up the idea, however, after a moment's reflection. There were no words in the Danequa language, nor concepts in the Danequa mind, by which he could explain the space-time machine and the world of the future to Tlaxcan. The cultures and customs and beliefs they had each known since childhood, stood between them—and yet Tlaxcan was one of the best friends that he had ever had, and

Mark hated to leave him without a word of good-by or an attempt at explanation.

Mark toyed with the idea of taking Tlaxcan back with him in the space-time machine, but he could see that it would never work out. Tlaxcan would be far more out of place in Mark's time than Mark was in his; he would be regarded as a freak, a Cro-Magnon in modern times, a newspaper sensation. And Tlaxcan was no freak; he was a human being, and entitled to a life of his own.

Mark looked around him at the Danequa, with the odd feeling of one who sees his own infinitely remote ancestors walking before him. Time travel played some funny tricks occasionally, and this was one of them. He knew the Danequa were in every respect his own ancestors. They were the people who had developed into the modern populations of Europe and England, and thus those who had largely colonized America. There probably were not very many of them at this relatively early time, and it was entirely possible that Mark was very distantly related to all of them, as their extremely distant descendant.

His mind stuck on the subject for a moment; it was difficult to figure it out to his own satisfaction. Even when you yourself had become the first real time traveler, time travel posed some unanswerable questions. For example, what would have happened if he had gone back in time only two years? He then could have looked up himself at the age of fifteen, and talked to himself. But if he had done that, wouldn't he have remembered it at seventeen before he had started back?

Or . . .

the Neanderthals had owned the earth. All the long years since the birth of Christ represented less than one-fiftieth as long a period as the one hundred thousand years the half-men had flourished.

Pity the Neanderthal, Mark thought, pity him but remember that you yourself have not equaled his record. How long would "modern" man last? Would he destroy himself with his unleashed technology? Was it just egotism that he fancied himself to be the end product of the evolution of intelligence? What future species might one day coldly replace humanity, even as humanity now was replacing the half-men?

But the Neanderthals were not gone yet, Mark reminded himself grimly. They were there, they were deadly, and they barred his way back to the space-time machine. Mark could predict, with some certainty, the outcome of the coming battle. The Dane qua, surely, would win. They were more intelligent, they had better weapons, and they had the advantage of surprise. The Neanderthals had no chance in the long run, even as the American Indian had had no chance against repeating rifles and disciplined armies. But predicting the general outlines of future events was not the same thing as predicting what would happen to the individuals involved in them. The Indians had lost, but they had taken many a white man into the shadows with them. The half-men would lose, but how many Danequa would die by their side?

During the night, the Danequa deployed their men. They had decided against a headlong charge into the valley of the half-men, preferring a plan that would enable them to take full advantage of the superior range of their bows and arrows. They could see that the ideal situation would be to deploy the Danequa archers just within arrow range, but too far away for the Mroxor spears to be effective. Theoretically, they could thus destroy the half-men without losing a man of their own.

Theories, however, have an unpleasant way of not working out under actual conditions. The Danequa leaders knew that a plan had to be flexible in order to function under battle conditions, and they knew too that the Neanderthals were not so stupid that they would permit themselves to stay in an impossible position. They would either charge the archers or they would retreat into their caves, where they would be safe as long as their food supply held out. Therefore, with quite remarkable skill, the Danequa had planned their movements to take the best possible advantage of the situation and the terrain.

One small party of Danequa archers filtered down to the head of the mountain pass and hid themselves among the rocks and pines. The other warriors stationed themselves along the high sides of the valley, where their bows could command the entrances to the Mroxor caves. Mark and Tlaxcan were high on the mountainside behind a boulder, the silent Fang lying quietly between them.

Night passed and the dawn came. Mark looked down into the valley before him and could not repress a shudder as the bestial half-men shuffled out of their dark caves and prepared to go about the day's activities. He remembered all too well the hours of horror he had experienced in that desolate pass, and he knew that only a miracle had saved him from death at the hands of the half-men. Had he come so far, dared so much, only to meet death at their hands at last?

Cutting clear through the babbling growls below them, the voice of Nranquar shouted a signal. Fang barked fiercely and Mark and Tlaxcan leaped to their feet. The Neanderthals were caught without a warning of any sort; the cold valley air was filled with a cloud of whizzing arrows before they even had time to arm themselves.

The squat Mroxor, their legs bent and their powerful bodies covered with pelts of dirty, matted hair, dropped like flies. Their screams and the cries of their women and children made the air hideous with sound. Half-men or not, their deaths were tragically horrible.

Mark took no part in the killing, for the good and simple reason that he had no bow and arrows and his spear was of no use at long range. He was saving his one precious shot for an emergency, and the emergency was not yet. Looking down from the heights, the Mroxor below looked like crumpling toys, gruesome miniature monsters falling on the valley floor.

But the half-men knew something about fighting themselves. They certainly had no lack of courage, and they rallied admirably under the storm of arrows. There was no panic-stricken retreat, no hysteria. Determined to make the best of things, the ugly creatures dashed into their caves and armed themselves with spears and axes and knives. Then, seeing all too well that they could be driven out of the caverns by hunger eventually, they regrouped and shuffled at full speed across the valley floor, trying to get out of the trap and into the open where they could fight man-to-man. It was not altogether an admirable plan, but no men think too clearly when their friends are dropping on all sides of them under a rain of death.

The Neanderthals did what they could, knowing that the battle was lost before it had ever started. They retreated across the valley floor, snarling and growling their hate, and they took their women and children with them. Only the very young who were too small to run were left beind. Even in the dawn of man, war was not a pleasant business.

The warriors of the Danequa, sensing victory and remembering the cold bodies of their own friends murdered by the hideous Mroxor, swarmed down from the sides of the mountain, driving the half-men across the valley floor. Mark and Tlaxcan ran side by side, with Fang yelping and barking ahead of them. The air shook with sounds and the shouts of men, and the Danequa ran unheeding over the still-warm corpses of the Neanderthals they had slain.

Quite suddenly, the rout stopped. Without any warning of any sort, six of the half-men stopped short, turned, and charged their attackers. The rest cut off down a hidden trail out of the valley, neatly evading the trap that had been set for them in the mouth of the valley where more Danequa bowmen waited.

Mark and Tlaxcan, a moment before trotting along in the flush of victory, found themselves fighting for their lives in the twinkling of an eye. The six Mroxor, swinging their stone axes in vicious circles around their bestial heads, plunged into their midst with snarls and cries that were more than animal-like in their ferocity. Savagely, they lashed out around them, and the Danequa line crumpled and stopped.

Tlaxcan threw away his bow and went after a

Mroxor with his knife. Mark jabbed one half-man with his lance, and then fell flat on his face to get out of the way of a whistling stone ax wielded by another. Fang jumped the monster, sinking his strong white teeth into his throat, and old Roqan stepped coolly back and pierced the shrieking Mroxor with an arrow. Mark got up and turned to help Tlaxcan, but there was no need. Tlaxcan had downed his antagonist, although he himself was smeared with blood that was not entirely his enemy's.

It was all over in seconds. The six Neanderthals lay dead on the field, and four of the Danequa were seriously injured. The Mroxor suicide attack had failed, as they, of course, had known it would. But the heroic rear guard action had served its purpose. During the milling confusion, the rest of the half-men had made good their escape from the valley.

Mark's heart sank within him. The Mroxor had fled out of the valley to the north, out across the great plains. They were doubly dangerous, maddened as they were by the loss of their friends, and they were still between Mark and the space-time machine.

"Come on!" shouted old Roqan, his eyes blazing. "Are the Danequa women that they will let the Mroxor slip through their fingers? After them!"

A roar of approval went up from the assembled warriors, and they charged in a mass out of the valley to pursue the fleeing half-men. Once more, however, the Mroxor had fooled them.

They were not all fleeing.

As the Danequa raced through the mouth of the valley, huge boulders pounded down on them from the hills above. There were not many of them, and the few half-men who had stayed behind promptly ducked back out of sight, but even a few boulders bouncing down into a pass choked with men are no joke. The shattering explosions of the smashing rocks threw the Danequa into momentary confusion again, and two warriors were crushed like bugs under the murderous barrage.

When they had recovered, the escaping Neanderthals had a good lead on them, and even as they watched, the half-men split into three groups, fanning out across the great plains and each group taking a different direction. With grim urgency now, the Danequa reorganized. A large party of warriors ran off at full speed to intercept the Mroxor bearing toward the east. They had to be stopped at all costs before they reached the almost unprotected valley of the Danequa, where the Danequa women and children were. A smaller group charged after the Mroxor heading west, and another party ran out across the plains directly toward the north.

Mark, Tlaxcan, and Nranquar were in the center group, with Fang racing at their side. The Neanderthals were running for their lives, snarling like elusive animals through the tall grass of the plains. The Danequa charged after them, trying desperately to get within arrow range. The pell-mell race settled down into a trotting run as it rapidly turned into an endurance contest.

For hours they forced themselves on through the tall grasses and the brilliant flowers, while the sun marched sedately through the blue sky, and the gentle breezes played unconcernedly across the earth. Mark was strong and hard now, but he was tiring speedily and nearing complete exhaustion. He could not run forever, and evening would be upon them soon, forcing them to turn back from their grim hunt. He forced himself to go on, however, knowing that every step took him closer to his long-awaited goal. The space-time machine, if only nothing had happened to it!

You'll never get another chance, his straining mind whispered, urging him on.

They were gaining on the half-men now. The Mroxor, hampered by their women and children, were losing ground. Determined to hold out until the saving night, the Mroxor suddenly split up again into still smaller groups. At an unspoken command, the Danequa peeled off their own units to follow them across the plains. Mark and Tlaxcan were left alone, two of the Danequa against two of the cornered Mroxor.

On and on they went, these four creatures playing out the most deadly game of all across the plains of the Ice Age. Fang's tongue lolled with weariness, and now the sun was dangerously low in the western sky. Mark forced every last ounce of strength into the race, every single atom of his being concentrated on catching those shambling half-men ahead of him. Unless they caught them before night, they would have to turn back or run the certain risk of ambush in the tall grass. And the space-time machine was so near—surely it was just ahead of them!

They were drawing nearer, the gap was closing. They were gaining, but could they make it in time?

The long shadows of evening began to creep across the plains . . .

through the fading light to wait for them. They were through running—they were ready to fight.

Tlaxcan skidded to a halt and whipped an arrow into his bow. Mark was unable to stop; he simply had to veer off to one side to avoid running right into a half-man's waiting spear. Heart pounding wildly, he slipped and fell in the tall grass. He hit rolling, and snatched out his .45 as he rolled. He came up on all fours, the .45 ready in his hand, and instantly was confronted by a terrible problem. Tlaxcan had not succeeded in loosing an arrow in time, and the more powerful Neanderthal had him down flat on the ground, trying to slit his throat with a stone knife. Tlaxcan was obviously nearly unconscious and his strength was slipping. The other Neanderthal was crouching low for the kill, moving toward Mark through the tall grass.

Mark had one bullet left in his .45.

He did not hesitate; there was no time to think. Mark took careful aim, squeezed the trigger, and the half-man threatening Tlaxcan dropped as though he had been clubbed with a crowbar. Mark at once threw the empty gun with all his might into the bestial face of the advancing Mroxor. The weapon struck home, staggering the Neanderthal for a moment. Mark leaped to his feet and grabbed up his spear, and was dismayed to see that the point had broken off in his fall.

The half-man recovered himself and moved in again, a stone knife in his hand. Mark gave ground, using the shaft of his broken lance as a fencing weapon to keep the Mroxor at bay. He jabbed desperately, backing all the while, knowing that he was no match for the Neanderthal in brute strength. If the half-man could once get his viselike hands on him, he would tear him to pieces.

Mark thrust and clubbed, keeping on the move. He could smell the Neanderthal's sweating nearness, see the red blood-lust in the thing's eyes as he stalked him. Mark's blood ran cold and he fought in a kind of daze, knowing that he was tired from his long run and that his strength was failing him.

He could not escape. He knew that now with icy certainty. He would have to stand and fight while some power was still left in his muscles. But he didn't fool himself. The barrel-chested Neanderthal could break him in two as easily as snapping a twig!

Mark had no choice. He stopped and stood his ground, using the spear shaft alternately as a jabbing weapon and as a light club. It was too light, however; time and again, he connected with a solid blow on the side of the half-man's hairy head, but the Mroxor just blinked his sunken eyes and kept on coming.

It was only a question of time. The Neanderthal had been waiting his chance, and when Mark's swing was just a trifle off its target, the half-man caught the spear shaft in his long-nailed, dirty hand and wrested it from Mark's grasp with one contemptuous wrench.

Mark felt the cold hand of death reach out for him once more. He stood facing the Neanderthal alone, without arms of any sort. He was too tired to run. His mind kept functioning somehow, telling him that at no cost must he allow the half-man to wrestle him, get him at too close quarters.

He would have to box him. The situation looked hopeless, but Mark was prepared to fight as long as life burned within him.

Smiling the grim smile of the hopeless, Mark suddenly stepped forward. With his left he feinted at the surprised half-man, and when the Neanderthal clumsily tried to catch his fist Mark came up from his toes with a sizzling right haymaker that caught the half-man on the point of his hair-matted jaw.

It was like hitting the side of the Empire State Building. The Neanderthal just shook his head slowly and moved on in for the kill. Mark had hit him with everything he had, and it hadn't been enough.

Frantically, he backed away, not taking his eyes off his foe. The half-man stalked him with a smothered fury, his hands opening and closing with unmistakable suggestiveness. Mark took a deep breath. He could go no further. He saw a jagged, heavy stone lying in the grass near him, but he knew that when he bent to pick it up the Mroxor would be on him like a flash and that would be that.

There was nothing else to do. Mark dived for the stone, and the Neanderthal snarled and leaped with him. Mark closed his eyes—and then opened them again in amazement.

The half-man never reached his prey. The wolf-dog, Fang, had launched himself through the air like a juggernaut, slamming into the thing and knocking it off balance. Fang had been with the fallen Tlaxcan, but now he had rejoined his master, rejoined him with a savage fury that had the Neanderthal fighting for his very life under an onslaught of powerful, snapping jaws that ripped and tore at his throat.

Mark jerked to his feet, swaying, the rock in his hand. The path to the space-time machine was now clear before him; he had only to run to it and get in, leaving Fang and Tlaxcan to their own devices. Mark did not even think about it, nor was it heroism on his part, or stupid bravery. It was just the way he was; he could no more have abandoned his friends than he could have sprouted wings and flown away into the heavens.

Mark charged at the snarling battle and took careful aim with his rock. The Neanderthal had Fang's throat in his hands now, crushing it like a vise. Fang held on with a death-hold, but his eyes were bulging piteously, begging Mark for help.

He got it. Mark hit the Neanderthal's skull with the jagged rock, pounding the rock down with all his might. The half-man still did not release the dog. Mark's rock-filled fist came down again—and again and again.

Maddened now by a drive he had not known he possessed, Mark snatched up the Neanderthal's stone knife where it had fallen in the grass and went in for the kill.

Exhausted, Mark sank down in the grass while Fang staggered to his feet and licked his face. Mark reached up and scratched the dog's ears, fighting to get his breath. He felt himself drifting down the night shadows; it was so pleasant lying in the warm grass . . .

Tlaxcan.

His memory returning, Mark got wearily to his feet and hurried back to his friend. Tlaxcan was sitting up on the ground, holding his head in his hands; the Neanderthal Mark had shot still sprawled beside him. Mark helped him to his feet.

"How do you feel?" he asked. "Are you all right?"

"I feel. . . That is enough in itself," Tlaxcan smiled. "Come, my friend, the night winds are almost upon us."

"I'm not going with you, Tlaxcan," Mark said slowly, his stomach hollow within him.

Tlaxcan looked at him, the smile vanishing from his face.

"I must go away," Mark said, trying to make Tlaxcan understand. "It is not that I wish to leave my friend, but I must go away."

Tlaxcan hesitated. "You will return, Mark?"

"Perhaps," Mark said, knowing that he was lying. He would never see Tlaxcan again.

The blood-red sun was very low in the west, only its upper tip still showing above the mountains, holding the night shadows at bay. The long grasses began to ripple under the whisper of the cool night wind.

Tlaxcan did not argue. No doubt his friend had good reasons for what he did, and it was not good to question a friend's action. Mark would go his way, and Tlaxcan would go his. Tlaxcan smiled again and placed his right hand on Mark's shoulder.

"Orn," he said simply. "We shall be brothers always."

"Orn," Mark echoed him. "We shall be brothers always."

With that, Tlaxcan turned without another word and walked eastward across the plains, starting the long journey back to his people and his home. He did not look back.

Fang sat quite still in the grass, looking up at Mark with questioning eyes. Mark scratched the wolf-dog's ears and smoothed the soft hair on the back of his neck.

"You too, old fellow," he told his dog. "This is your home. Go with Tlaxcan. Do you understand? Go with Tlaxcan!"

He pointed after his friend across the fields. Fang whined deep in his throat and wagged his bushy tail hopefully.

"No," Mark said. "I must go alone. Go with Tlaxcan!"

The wolf-dog seemed to understand, with that intuitive knowledge of the strange ways of their masters that good dogs always have. He looked sorrowfully at Mark with deep and liquid eyes and trotted slowly away into the gathering gloom, following Tlaxcan through the shadows.

They were gone. Mark was alone.

With a terrible loneliness buried deep within him, Mark set off northward toward the gray sphere of the space-time machine, invisible now in the darkness. The cold wind blew in his face, and he felt like an ant crawling across the earth, alone and unprotected.

He remembered the dream he had had, so long ago. He had been racing across this gray world, the half-men snarling behind him. The gray grass had shimmered beneath a gray-smoke wind that whipped and billowed before his very eyes. And ahead of him—a great gray sphere, waiting on a cold, gray plain. Even as now ...

Except, of course, that there were no Neanderthals around now. Or were there? Had some of them doubled back? What could he do, without any weapon but the empty .45 he had picked up and the stone knife of the Mroxor?

Suddenly, the night seemed full of sounds. Ominous sounds. . .

Mark redoubled his pace, and the bulge of the spacetime machine loomed up out of the grayness before him. It was just as he had left it, a lifetime ago, silent and ghostlike under the first stars of the night.

A cold chill ran through him as he remembered the monster half-man who had waited inside the machine in his dream. He told himself that such thoughts were nonsense, but still it was all that he could do to throw the gray switch that activated the entry port. He held his breath. If the port failed to open—

With a mechanical hiss, a strange, foreign sound here on the plains of the darkening Ice Age, the circular door slid open. The interior glowed with soft white light, spilling out like cold, shining oil into the night. Mark stepped through the entry port, feeling nervous and unreal with the smooth metallic sphere all around him.

The space-time machine was empty. Mark threw the inside switch, his hands clumsy on the almost-forgotten machinery, and the circular entry port hissed shut behind him, sealing him in. All was as he had left it, except that the yellow caution light in the control panel, signifying that the machine was rebuilding its energy potential, was out.

The green light looked at him like an inviting eye from the panel. The space-time machine was ready to go.

Wiping his sweating hands on the fur of his clothing, Mark examined the timing dials before him. He had to be very careful now, he knew. He wanted to set the space-time machine to arrive back at his uncle's lodge as shortly as possible after he had first left, in order to spare Doctor Nye unnecessary, frantic worry. His uncle was in good health, and was far from being an old man, but Mark well knew that he was the only thing that really counted in Doctor Nye's life. He lived only for Mark and for his trip back to ancient Rome, a trip that Mark had unwittingly deprived him of. He had lost his dream, and if he lost his adopted son as well . . .

The small pointer, like the fine second hand of a watch, was exact almost to the second, and Mark decided that fifteen minutes would be an acceptable safety margin. That would not give his uncle time to worry unduly about him, and would give Mark enough of a margin to prevent a spine-chilling possibility of getting back too soon.

For example, he thought, what would happen if he got back to 1953 fifteen minutes before he had left? Would there be two Marks in the basement of Doctor Nye's house, and two space-time machines? What would happen when the explosion occurred and there could only be one? Or would he simply somehow fade into that other Mark, waiting there with his uncle, and talk with him until that fatal phone call and the blowup —and then go back in space-time again, repeating his adventures in the Ice Age endlessly, forever? Would he be destined always to go back too soon, caught up in an eternal circle of his own devising?

These were unanswerable questions, and they were questions that Mark was fully content to leave unanswered. He took his time and set the dial with infinite precision. It had been nine o'clock when the space-time machine had left on its strange journey, and now he set it for the return at precisely nine-fifteen. He adjusted the other dials with equal care for the day and the month and the year and then he paused.

There was nothing else to do but throw the knife

the intricate adjustments needed to travel through space-time in the twinkling of an eye; it would have taken a human being a lifetime to figure them out. His uncle had once told him that space-time travel would have been an impossibility without the robot computers of cybernetics . . .

Even with his eyes closed, Mark could feel the red eye staring at him through the gray fog. The humming vibrations buzzed through his brain, and he found it hard to relax. How strange it was, he thought, that this most fascinating adventure of man was in a very real sense monotonous while you were going through it. There was absolutely nothing to see in the space-time machine, and very little to do.

It was ironic, too, that he had no idea what time it was. Here in the midst of the most finely adjusted timing mechanisms ever devised by man, he had no way of measuring the time interval within the space-time machine itself. Subjective time, the mind's own reckoning of passing time, was apt to be a tricky and unreliable business. Mark could not tell how long he lay on the floor of the sphere; it might have been long minutes, or short hours, or even speeding days.

Many times, he opened his eyes, only to see nothing. There was only the gray mist and the red eye and the humming of the vibrations. There was only an electric nothingness, and within it, lost and invisible, the colossal span of history marching by on ghost-feet into the shadows that never were.

Time passed, inside and out, and Mark dozed fitfully. As it had been the first time, the first impression he had that the space-time machine had stopped came when he suddenly noticed a complete absence of sound. There was nothing. It was the dead hush of a tomb.

Mark opened his eyes. The red light in the control panel had gone off, and the yellow light had replaced it. Mark jumped to his feet, his heart hammering against his chest. His palms were wet with sweat as he threw the small switch that governed the exit. The circular entry port hissed back.

Holding his breath, Mark stepped outside.

"Stop right there," a voice said coldly. "Just stop right there."

Mark crouched back against the space-time machine, his powerful fists clenching for action. His unaccustomed eyes blinked in the bright light that streamed into his face. What had happened? Where was he?

What could have gone wrong?

His vision cleared. Mark stared around him, and laughed almost hysterically with relief. He was back in his uncle's lead-lined room where he had started, and through the open door in the wall beyond he could see the equipment-strewn basement of Doctor Nye's lodge. And the white-haired man before him, a wicked-looking wrench in his hand, was Doctor Nye.

"Uncle Bob," Mark said softly. "Don't you know me?"

Doctor Nye stared and stared, unable to believe his eyes. For the first time, Mark realized what a strange spectacle he must present, and how different he was from the boy who had left this room an infinity ago. He was bronzed and powerful, and his blue jeans and wool shirt had been replaced by a covering of furs. Hide sandals protected his feet, and a stone knife was stuck in the belt around his waist. His long hair was tied in place with a rawhide thong, and his eyes were no longer the eyes of a boy. Doctor Nye dropped the wrench.

"Mark!" he gasped. "Mark—"

Doctor Nye embraced his adopted son with a trembling gladness and then stepped back again to stare at him. "I just can't believe it, Mark," he whispered. He looked at his watch. "It's nine-fifteen—you've only been gone fifteen minutes in this time. I was hoping against hope . . ."

Momentarily overcome with emotion, Doctor Nye stopped, running his hands through his white hair as if to get his mind under control by sheer physical force. Mark put his arm around his uncle's shoulder, ignoring a strong impulse simply to put his right hand on his shoulder, Danequa fashion. He understood that it had all happened so fast for his uncle that he was unnerved by it all. He had, after all, only discovered his nephew's absence a few minutes ago, and here Mark was back again, to all intents and appearances a grown man. It was characteristic of Doctor Nye that he obviously had not even thought of the loss of his space-time machine, or of his vanished dream to go back to the Rome of legend. His every thought had been of his boy.

"Upstairs," Doctor Nye said finally, shaking himself. "Let's go upstairs."

Together, they walked out of the lead-lined room that housed the space-time machine and through the basement laboratory. Mark noticed that the machine was approximately two feet nearer the door than it had been before; an error of two feet and a few sec-

onds in a fifty-thousand-plus years' journey through space-time was nothing to be ashamed of. They climbed the stairs, went through the kitchen where the roast was still warming in the oven and die pot of coffee Mark had started a half-hour or so ago was bubbling merrily, and entered the sitting room. There was the bust of Caesar by the lamp on the table, the long shelves full of books, the Navajo rugs on the floor, the walls of lightly varnished pine. It was all just as he had left it a few short minutes ago, and it was all strange and unreal to the Mark who had traveled across the ages, as though something remembered from a dream.

Fang, who had been awakened earlier by the explosion, stood bolt upright in the best armchair in the house and growled curiously at Mark. Who was this intruder with the fur clothes and the long hair tied with rawhide? Fang bristled, and barked shrilly. Then he eyed Mark more closely, and the stump of his tail began to wag. Uncertainly, he leaped off the chair and the golden-brown cocker spaniel puppy trotted across the room and sniffed Mark suspiciously. Satisfied then, as Mark scratched his ears, Fang wagged the stump of his tail again and returned to his armchair. He couldn't quite figure it out, but he trusted his sense of smell more than he did his eyes. He was not excessively glad to see Mark, of course—after all, his master had just gone downstairs a few minutes before.

Doctor Nye sank into a chair, and Mark did likewise. The soft cushions felt curiously unpleasant; he felt as though he were sinking through to the floor.

Nervously, Mark clenched and unclenched his fists, trying to get used to his own home again.

"How long were you gone, Mark?" Doctor Nye asked finally.

"I'm not sure," Mark said. "A few months, I think." The English felt awkward in his mouth, like a foreign tongue.

"Fifty thousand years before Christ," mused Doctor Nye, who had set the dials himself. And then, oddly: "Are you hungry?"

Mark smiled. "No. What happened—was it the rocket?"

Doctor Nye nodded. "The test rocket went off-course and blew up in the hills near here," he said. "It was a miracle no one was hurt."

Mark shifted uncomfortably in the silence. The very concept of such things as "rockets" was strange to him now; his whole mental set had changed, his mind was oriented to a different set of conditions, and he felt like an intruder in his own home.

"I would never have forgiven myself, Mark, if—"

Mark shook his head. "It wasn't your fault, Uncle Bob," he said. "And I'm grateful, really. I can't talk about it now, but it was the most wonderful experience I've ever known."

Doctor Nye nodded, understanding. "There'll be plenty of time to talk later," he said quietly.

"Uncle Bob — I'm so sorry — the space-time machine . . ."

"Forget it, son," Doctor Nye said, rising and placing his hand on Mark's shoulder in a gesture strangely like that of the Danequa. "Perhaps, one day, I can rebuild it again. What man has done once, man can do again.

You are all that counts, Mark. I do not think that the space-time machine was wasted. When you left here fifteen minutes ago, you were a boy. Now you are a man. Your eyes are open, son, and that is something beyond any price."

Mark sat silently for a moment, trying to get himself adjusted to things. He looked at little Fang dozing in the armchair. How different the cocker spaniel was from the wolf-dog he had left in the shadows of the Ice Age!

"It's stopped raining, hasn't it?" he asked after a short time. "Yes."

"Let's go outside, Uncle Bob. Let's just go out and walk around for a while."

"Good idea, son," Doctor Nye smiled. "But first I think you better change your clothes, before someone takes a pot shot at you for looking like a man from Mars or something."

Mark grinned back, beginning to relax a little, and hurried up to change. His own clothes were too small for him, but he made them do. His feet, however, flatly refused to suffer through a pair of shoes, so he kept his Danequa sandals on. He glanced at the man who looked back at him out of his mirror, hardly recognizing him. He felt like a spy, an alien, in his own room and he left rapidly and rejoined his uncle in the sitting room.

"That's better," Doctor Nye approved, puffing on his pipe. "Come on. We'll walk up to the Point."

They went outside, into the cool night air and the silence, and Mark Nye instantly relaxed. There was the smell of the familiar pines in the air, and the freshly washed earth was heavy with clean scent. The black clouds had broken above them, and the frosted stars twinkled coldly in the black sky. A full moon raced along behind the scudding clouds, turning them into a silver sea and itself into a circular ship of frozen ice that sailed in and out among them. Mark breathed deeply, glad to be alive.

Neither man spoke. They walked along the path through the moonlit night until they came to the Point, and there they stopped. The Point was an outcropping of rock that looked down into the light-pointed valley below. It was free of trees, and the soft night wind whispered around it eerily. A transport plane, high in the sky, winged along above them, its engines muted by distance, its red and green running lights blinking in the stars.

The full moon sailed clear of the silver-flecked clouds, and Mark watched it with a heavy heart. His friends were dead, dead and ashes in the mists of time. Tlaxcan smiled no more, and little Tlax had lived and dreamed and died and was gone forever. Nranquar, and Roqan, and the proud Qualxen—where were they now?

Gone. Lost in the dust of ages . . . Mark looked at his uncle, puffing his pipe in silence beneath the moon. He was glad to be back with him again. This, after all, was where he belonged. He had no choice. This was his world, with all its problems, and it was here that his life must be lived. And yet-There was the full moon. How long ago had it been that he sang the song of die Danequa beneath that same full moon, with the excitement of the quaro hunt