>>> The Cruel Sky

By midnight, the summit of Everest was only a hundred yards away, a pyramid of snow, pale and ghostly in the light of the rising Moon. The sky was cloudless, and the wind that had been blowing for days had dropped almost to zero. It must be rare indeed for the highest point on Earth to be so calm and peaceful; they had chosen their time well.

Perhaps too well, thought George Harper; it had been almost disappointingly easy. Their only real problem had been getting out of the hotel without being observed. The management objected to unauthorized midnight excursions up the mountain; there could be accidents, which were bad for business.

But Dr. Elwin was determined to do it this way, and he had the best of reasons, though he never discussed them. The presence of one of the world's most famous scientists-and certainly the world's most famous cripple-at Hotel Everest during the height of the tourist season had already aroused a good deal of polite surprise. Harper had allayed some of the curiosity by hinting that they were engaged in gravity measurements, which was at least part of the truth. But a part of the truth that, by this time, was vanishingly small.

Anyone looking at Jules Elwin now, as he forged steadily toward the twenty-nine-thousand-foot level with fifty pounds of equipment on his shoulders, would never have guessed that his legs were almost useless. He had been born a victim of the 1961 thalidomide disaster, which had left more than ten thousand partially deformed children scattered over the face of the world. Elwin was one of the lucky ones. His arms were quite normal, and had been strengthened by exercise until they were considerably more powerful than most men's. His legs, however, were mere wisps of flesh and bone. With the aid of braces, he could stand and even totter a few uncertain steps, but he could never really walk.

Yet now he was two hundred feet from the top of Everest.... A travel poster had started it all, more than three years ago. As a junior computer programmer in the Applied Physics Division, George Harper knew Dr. Elwin only by sight and by reputation. Even to those working directly under him, Astrotech's brilliant Director of Research was a slightly remote personality, cut off from the ordinary run of men both by his body and by his mind. He was neither liked nor disliked, and, though he was admired and pitied, he was certainly not envied.

Harper, only a few months out of college, doubted if the Doctor even knew of his existence, except as a name on an organization chart. There were ten other programmers in the division, all senior to him, and most of them had never exchanged more than a dozen words with their research director. When Harper was co-opted as messenger boy to carry one of the classified files into Dr. Elwm's office, he expected to be in and out with nothing more than a few polite formalities.

That was almost what happened. But just as he was leaving, he was stopped dead by the magnificent panorama of Himalayan peaks covering half of one wall. It had been placed where Dr. Elwin could see it whenever he looked up from his desk, and it showed a scene that Harper knew very well indeed, for he had photographed it himself, as an awed and slightly breathless tourist standing on the trampled snow at the crown of Everest.

There was the white ridge of Kanchenjunga, rearing through the clouds almost a hundred miles away. Nearly in line with it, but much nearer, were the twin peaks of Makalu; and closer still, dominating the foreground, was the immense bulk of Lhotse, Everest's neighbor and rival. Farther around to the west, flowing down valleys so huge that the eye could not appreciate their scale, were the jumbled ice rivers of the Khumbu and Rongbuk glaciers. From this height, their frozen wrinkles looked no larger than the furrows in a plowed field; but those ruts and scars of iron-hard ice were hundreds of feet deep.

Harper was still taking in that spectacular view, reliving old memories, when he heard Dr. Elwin's voice behind him.

"You seem interested. Have you ever been there?"

"Yes, Doctor. My folks took me after I graduated from high school. We stayed at the hotel for a week, and thought we'd have to go home before the weather cleared. But on the last day the wind stopped blowing, and about twenty of us made it to the summit. We were there for an hour, taking pictures of each other."

Dr. Elwin seemed to digest this information for rather a long time. Then he said, in a voice that had lost its previous remoteness and now held a definite undercurrent of excitement: "Sit down, Mr.-ah-Harper. I'd like to hear more."

As he walked back to the chair facing the Director's big uncluttered desk, George Harper found himself somewhat puzzled. What he had done was not in the least unusual; every year thousands of people went to the Hotel Everest, and about a quarter of them reached the mountain's summit. Only last year, in fact, there had been a much-publicized presentation to the ten-thousandth tourist to stand on the top of the world. Some cynics had commented on the extraordinary coincidence that Number 10,000 had just happened to be a rather well known video starlet.

There was nothing that Harper could tell Dr. Elwin that he couldn't discover just as easily from a dozen other sources-the tourist brochures, for example. However, no young and ambitious scientist would miss this opportunity to impress a man who could do so much to help his career. Harper was neither coldly calculating nor inclined to dabble in office politics, but he knew a good chance when he saw one.

"Well, Doctor," he began, speaking slowly at first as he tried to put his thoughts and memories in order, "the jets land you at a little town called Namchi, about twenty miles from the mountain. Then the bus takes you along a spectacular road up to the hotel, which overlooks the Khumbu Glacier. It's at an altitude of eighteen thousand feet, and there are pressurized rooms for anyone who finds it hard to breathe. Of course, there's a medical staff in attendance, and the management won't accept guests who aren't physically fit. You have to stay at the hotel for at least two days, on a special diet, before you're allowed to go higher.

"From the hotel you can't actually see the summit, because you're too close to the mountain, and it seems to loom right above you. But the view is fantastic. You can see Lhotse and half a dozen other peaks. And it can be scary, too-especially at night. The wind is usually howling somewhere high overhead, and there are weird noises from the moving ice. It's easy to imagine that there are monsters prowling around up in the mountains....

"There's not much to do at the hotel, except to relax and watch the scenery, and to wait until the doctors give you the go-ahead. In the old days it used to take weeks to acclimatize to the thin air; now they can make your blood count shoot up to the right level in forty-eight hours. Even so, about half the visitors-mostly the older ones-decide that this is quite high enough for them.

"What happens next depends on how experienced you are, and how much you're willing to pay. A few expert climbers hire guides and make their own way to the top, using standard mountaineering equipment. That isn't too difficult nowadays, and there are shelters at various strategic spots. Most of these groups make it. But the weather is always a gamble, and every year a few people get killed.

"The average tourist does it the easier way. No aircraft are allowed to land on Everest itself, except in emergencies, but there's a lodge near the crest of Nuptse and a helicopter service to it from the hotel. From the lodge it's only three miles to the summit, via the South Col-an easy climb for anyone in good condition, with a little mountaineering experience. Some people do it without oxygen, though that's not recommended. I kept my mask on until I reached the top; then I took it off and found I could breathe without much difficulty."

"Did you use filters or gas cylinders?"

"Oh, molecular filters-they're quite reliable now, and increase the oxygen concentration over a hundred per cent. They've simplified high-altitude climbing enormously. No one carries compressed gas any more."

"How long did the climb take?"

"A full day. We left just before dawn and were back at nightfall. That would have surprised the old-timers. But of course we were starting fresh and traveling light. There are no real problems on the route from the lodge, and steps have been cut at all the tricky places. As I said, it's easy for anyone in good condition."

The instant he repeated those words. Harper wished that he had bitten off his tongue. It seemed incredible that he could have forgotten who he was talking to, but the wonder and excitement of that climb to the top of the world had come back so vividly that for a moment he was once more on that lonely, wind-swept peak.

The one spot on Earth where Dr. Elwin could never stand....

But the scientist did not appear to have noticed-or else he was so used to such unthinking tactlessness that it no longer bothered him. Why, wondered Harper, was he so interested in Everest? Probably because of that very inaccessibility; it stood for all that had been denied to him by the accident of birth.

Yet now, only three years later, George Harper paused a bare hundred feet from the summit and drew in the nylon rope as the Doctor caught up with him. Though nothing had ever been said about it, he knew that the scientist wished to be the first to the top. He deserved the honor, and the younger man would do nothing to rob him of it.

"Everything O.K.?" he asked as Dr. Elwin drew abreast of him. The question was quite unnecessary, but Harper felt an urgent need to challenge the great loneliness that now surrounded them. They might have been the only men in all the world; nowhere amid this white wilderness of peaks was there any sign that the human race existed.

Elwin did not answer, but gave an absent-minded nod as he went past, his shining eyes fixed upon the summit. He was walking with a curiously stiff-legged gait, and his feet made remarkably little impression in the snow. And as he walked, there came a faint but unmistakable whine from the bulky backpack he was carrying on his shoulders.

That pack, indeed, was carrying him-or three-quarters of him. As he forged steadily along the last few feet to his once-impossible goal. Dr. Elwin and all his equipment weighed only fifty pounds. And if that was still too much, he had only to turn a dial and he would weigh nothing at all.

Here amid the Moon-washed Himalayas was the greatest secret of the twenty-first century. In all the world, there were only five of these experimental Elwin Levitators, and two of them were here on Everest.

Even though he had known about them for two years, and understood something of their basic theory, the "Lewies"-as they had soon been christened at the lab-still seemed like magic to Harper. Their power-packs stored enough electrical energy to lift a two-hundred-and-fifty-pound weight through a vertical distance of ten miles, which gave an ample safety factor for this mission. The lift-and-descend cycle could be repeated almost indefinitely as the units reacted against the Earth's gravitational field. On the way up, the battery discharged; on the way down, it was charged again. Since no mechanical process is completely efficient, there was a slight loss of energy on each cycle, but it could be repeated at least a hundred times before the units were exhausted.

Climbing the mountain with most of their weight neutralized had been an exhilarating experience. The vertical tug of the harness made it feel that they were hanging from invisible balloons, whose buoyancy could be adjusted at will. They needed a certain amount of weight in order to get traction on the ground, and after some experimenting had settled on twenty-five per cent. With this, it was as easy to ascend a one-in-one slope as to walk normally on the level.

Several times they had cut their weight almost to zero to rise hand over hand up vertical rock faces. This had been the strangest experience of all, demanding complete faith in their equipment. To hang suspended in mid-air, apparently supported by nothing but a box of gently humming electronic gear, required a considerable effort of will. But after a few minutes, the sense of power and freedom overcame all fear; for here indeed was the realization of one of man's oldest dreams.

A few weeks ago one of the library staff had found a line from an early twentieth-century poem that described their achievement perfectly: "To ride secure the cruel sky." Not even birds had ever possessed such freedom of the third dimension; this was the real conquest of space. The Levitator would open up the mountains and the high places of the world, as a lifetime ago the aqualung had opened up the sea. Once these units had passed their tests and were mass-produced cheaply, every aspect of human civilization would be changed. Transport would be revolutionized. Space travel would be no more expensive than ordinary flying; all mankind would take to the air. What had happened a hundred years earlier with the invention of the automobile was only a mild foretaste of the staggering social and political changes that must now come.

But Dr. Elwin, Harper felt sure, was thinking of none of these in his lonely moment of triumph. Later, he would receive the world's applause (and perhaps its curses), yet it would not mean as much to him as standing here on Earth's highest point. This was truly a victory of mind over matter, of sheer intelligence over a frail and crippled body. All the rest would be anticlimax.

When Harper joined the scientist on the flattened, snowcovered pyramid, they shook hands with rather formal stiffness, because that seemed the right thing to do. But they said nothing; the wonder of their achievement, and the panorama of peaks that stretched as far as the eye could see in every direction, had robbed them of words.

Harper relaxed in the buoyant support of his harness and slowly scanned the circle of the sky. As he recognized them, he mentally called off the names of the surrounding giants: Makalu, Lhotse, Baruntse, Cho Oyu, Kanchenjunga.... Even now scores of these peaks had never been climbed. Well, the Lewies would soon change that.

There were many, of course, who would disapprove. But back in the twentieth century there had also been mountaineers who thought it was "cheating" to use oxygen. It was hard to believe that, even after weeks of acclimatization, men had once attempted to reach these heights with no artificial aids at all. Harper remembered Mallory and Irvine, whose bodies still lay undiscovered perhaps within a mile of this very spot.

Behind him. Dr. Elwin cleared his throat.

"Let's go, George," he said quietly, his voice muffled by the B oxygen filter. "We must get back before they start looking for us." | With a silent farewell to all those who had stood here before them, they turned away from the summit and started down the gentle slope. The night, which had been brilliantly clear until now, was becoming darker; some high clouds were slipping across the face of the Moon so rapidly that its light switched on and off in a manner that sometimes made it hard to see the route. Harper did not like the look of the weather and began mentally to rearrange their plans. Perhaps it would be better to aim for the shelter on the South Col, rather than attempt to reach the lodge. But he said nothing to Dr. Elwin, not wishing to raise any false alarms.

Now they were moving along a knife-edge of rock, with utter darkness on one side and a faintly glimmering snowscape on the other. This would be a terrible place. Harper could not help thinking, to be caught by a storm.

He had barely shaped the thought when the gale was upon them. From out of nowhere, it seemed, came a shrieking blast of air, as if the mountain had been husbanding its strength for this moment. There was no time to do anything; even had they possessed normal weight, they would have been swept off their feet. In seconds, the wind had tossed them out over shadowed, empty blackness.

It was impossible to judge the depths beneath them; when Harper forced himself to glance down, he could see nothing. Though the wind seemed to be carrying him almost horizontally, he knew that he must be falling. His residual weight would be taking him downward at a quarter of the normal speed. But that would be ample; if they fell four thousand feet, it would be poor consolation to know that it would seem only one thousand.

He had not yet had time for tear-that would come later, if he survived-and his main worry, absurdly enough, was that the expensive Levitator might be damaged. He had completely forgotten his partner, for in such a crisis the mind can hold only one idea at a time. The sudden jerk on the nylon rope filled him with puzzled alarm. Then he saw Dr. Elwin slowly revolving around him at the end of the line, like a planet circling a sun.

The sight snapped him back to reality, and to a consciousness of what must be done. His paralysis had probably lasted only a fraction of a second. He shouted across the wind: "Doctor! Use emergency lift!"

As he spoke, he fumbled for the seal on his control unit, tore it open, and pressed the button.

At once, the pack began to hum like a hive of angry bees. He felt the harness tugging at his body as it tried to drag him up into the sky, away from the invisible death below. The simple arithmetic of the Earth's gravitational field blazed in his mind, as if written in letters of fire. One kilowatt could lift a hundred kilograms through a meter every second, and the packs could convert energy at a maximum rate of ten kilowatts-though they could not keep this up for more than a minute. So allowing for his initial weight reduction, he should lift at well over a hundred feet a second.

There was a violent jerk on the rope as the slack between them was taken up. Dr. Elwin had been slow to punch the emergency button, but at last he, too, was ascending. It would be a race between the lifting power of their units and the wind that was sweeping them toward the icy face of Lhotse, now scarcely a thousand feet away.

That wall of snow-streaked rock loomed above them in the moonlight, a frozen wave of stone. It was impossible to judge their speed accurately, but they could hardly be moving at less than fifty miles an hour. Even if they survived the impact, they could not expect to escape serious injury; and injury here would be as good as death.

Then, just when it seemed that a collision was unavoidable, the current of air suddenly shot skyward, dragging them with it. They cleared the ridge of rock with a comfortable fifty feet to spare. It seemed like a miracle but, after a dizzying moment of relief, Harper realized that what had saved them was only simple aerodynamics. The wind had to rise in order to clear the mountain; on the other side, it would descend again. But that no longer mattered, for the sky ahead was empty.

Now they were moving quietly beneath the broken clouds. Though their speed had not slackened, the roar of the wind had suddenly died away, for they were traveling with it through emptiness. They could even converse comfortably, across the thirty feet of space that still separated them.

"Dr. Elwin," Harper called, "are you O.K.?"

"Yes, George," said the scientist, perfectly calmly. "Now what do we do?"

"We must stop lifting. If we go any higher, we won't be able to breathe-even with the filters."

"You're right. Let's get back into balance."

The angry humming of the packs died to a barely audible electric whine as they cut out the emergency circuits. For a few minutes they yo-yoed up and down on their nylon rope-first one uppermost, then the other-until they managed to get into trim.

When they had finally stabilized, they were drifting at a little below thirty thousand feet. Unless the Lewies failed-which, after their overload, was quite possible-they were out of immediate danger. Their troubles would start when they tried to return to Earth. No men in all history had ever greeted a stranger dawn. Though they were tired and stiff and cold, and the dryness of the thin air made every breath rasp in their throats, they forgot all these discomforts as the first dim glow spread along the jagged eastern horizon. The stars faded one by one; last to go, only minutes before the moment of daybreak, was the most brilliant of all the space stations-Pacific Number Three, hovering twenty-two thousand miles above Hawaii. Then the sun lifted above a sea of nameless peaks, and the Himalayan day had dawned.

It was like watching sunrise on the Moon. At first, only the highest mountains caught the slanting rays, while the surrounding valleys remained flooded with inky shadows. But slowly the line of light marched down the rocky slopes, and more and more of this harsh, forbidding land climbed into the new day.

Now, if one looked hard enough, it was possible to see signs of human life. There were a few narrow roads, thin columns of smoke from lonely villages, glints of reflected sunlight from monastery roofs. The world below was waking, wholly unaware of the two spectators poised so magically fifteen thousand feet above. During the night, the wind must have changed direction several times, and Harper had no idea where they were. He could not recognize a single landmark. They could have been anywhere over a five-hundred-mile-long strip of Nepal and Tibet.

The immediate problem was to choose a landing place-and that soon, for they were drifting rapidly toward a jumble of peaks and glaciers where they could hardly expect to find help. The wind was carrying them in a northeasterly direction, toward China. If they floated over the mountains and landed there, it might be weeks before they could get in contact with one of the U.N. Famine Relief Centers and find their way home. They might even be in some personal danger, if they descended out of the sky in an area where there was only an illiterate and superstitious peasant population.

"We'd better get down quickly," said Harper. "I don't like the look of those mountains." His words seemed utterly lost in the void around them. Although Dr. Elwin was only ten feet away, it was easy to imagine that his companion could not hear anything he said. But at last the Doctor nodded his head, in almost reluctant agreement.

"I'm afraid you're right-but I'm not sure we can make it, with this wind. Remember-we can't go down as quickly as we can rise."

That was true enough; the power-packs could be charged at only a tenth of their discharge rate. If they lost altitude and pumped gravitational energy back into them too fast, the cells would overheat and probably explode. The startled Tibetans (or Nepalese?) would think that a large meteorite had detonated in their sky. And no one would ever know exactly what had happened to Dr. Jules Elwin and his promising young assistant.

Five thousand feet above the ground, Harper began to expect the explosion at any moment. They were falling swiftly, but not swiftly enough; very soon they would have to decelerate, lest they hit at too high a speed. To make matters worse, they had completely miscalculated the air speed at ground level. That infernal, unpredictable wind was blowing a near-gale once more. They could see streamers of snow, torn from exposed ridges, waving like ghostly banners beneath them. While they had been moving with the wind, they were unaware of its power; now they must once again make the dangerous transition between stubborn rock and softly yielding sky.

The air current was tunneling them into the mouth of a canyon. There was no chance of lifting above it. They were committed, and would have to choose the best landing place they could find. The canyon was narrowing at a fearsome rate. Now it was little more than a vertical cleft, and the rocky walls were sliding past at thirty or forty miles an hour. From time to time random eddies would swing them to the right, then the left; often they missed collisions by only a few feet. Once, when they were sweeping scant yards above a ledge thickly covered with snow, Harper was tempted to pull the quick-release that would jettison the Levitator. But that would be jumping from the frying pan into the fire: they might get safely back onto firm ground only to find themselves trapped unknown miles from all possibility of help.

Yet even at this moment of renewed peril, he felt very little fear. It was all like an exciting dream-a dream from which he would presently wake up to find himself safely in his own bed. This fantastic adventure could not really be happening to him....

"George!" shouted the Doctor. "Now's our chance-if we can snag that boulder!"

They had only seconds in which to act. At once, they both began to play out the nylon rope, until it hung in a great loop beneath them, its lowest portion only a yard above the racing ground. A large rock, some twenty feet high, lay exactly in their line of flight; beyond it, a wide patch of snow gave promise of a reasonably soft landing.

The rope skittered over the lower curves of the boulder; seemed about to slip clear, then caught beneath an overhang. Harper felt the sudden jerk. He was swung around like a stone on the end of a sling.

I never thought that snow could be so hard, he told himself. After that there was a brief and brilliant explosion of light; then nothing.

He was back at the university, in the lecture room. One of the professors was talking, in a voice that was familiar, yet somehow did not seem to belong here. In a sleepy, halfhearted fashion, he ran through the names of his college instructors. No, it was certainly none of them. Yet he knew the voice so well, and it was undoubtedly lecturing to someone.

". . . still quite young when I realized that there was something wrong with Einstein's Theory of Gravitation. In particular, there seemed to be a fallacy underlying the Principle of Equivalence. According to this, there is no way of distinguishing between the effects produced by gravitation and those of acceleration.

"But this is clearly false. One can create a uniform acceleration; but a uniform gravitational field is impossible, since it obeys an inverse square law, and therefore must vary even over quite short distances. So tests can easily be devised to distinguish between the two cases, and this made me wonder if . . ."

The softly spoken words left no more impression on Harper's mind than if they were in a foreign language. He realized dimly that he should understand all this, but it was too much trouble to look for the meaning. Anyway, the first problem was to decide where he was.

Unless there was something wrong with his eyes, he was in complete darkness. He blinked, and the effort brought on such a splitting headache that he gave a cry of pain.

"George! Are you all right?"

Of course! That had been Dr. Elwin's voice, talking softly there in the darkness. But talking to whom?

"I've got a terrible headache. And there's a pain in my side when I try to move. What's happened? Why is it dark?"

"You've had concussion-and I think you've cracked a rib.

Don't do any unnecessary talking. You've been unconscious all day. It's night again, and we're inside the tent. I'm saving our batteries."

The glare from the flashlight was almost blinding when Dr. Elwin switched it on, and Harper saw the walls of the tiny tent around them. How lucky that they had brought full mountaineering equipment, just in case they got trapped on Everest. But perhaps it would only prolong the agony....

He was surprised that the crippled scientist had managed, without any assistance, to unpack all their gear, erect the tent, and drag him inside. Everything was laid out neatly: the first-aid kit, the concentrated-food cans, the water containers, the tiny red gas cylinders for the portable stove. Only the bulky Levitator units were missing; presumably they had been left outside to give more room.

"You were talking to someone when I woke up," Harper said.

"Or was I dreaming?" Though the indirect light reflected from the walls of the tent made it hard to read the other's expression, he could see that Elwin was embarrassed. Instantly, he knew why, and wished that he had never asked the question.

The scientist did not believe that they would survive. He had been recording his notes, in case their bodies were ever discovered. Harper wondered bleakly if he had already recorded his last will and testament.

Before Elwin could answer, he quickly changed the subject. "Have you called Lifeguard?"

"I've been trying every half hour, but I'm afraid we're shielded by the mountains. I can hear them, but they don't receive us." Dr. Elwin picked up the little recorder-transceiver, which he had unstrapped from its normal place on his wrist, and switched it on.

"This is Lifeguard Four," said a faint mechanical voice, "listening out now."

During the five-second pause, Elwin pressed the SOS button, then waited.

"This is Lifeguard Four, listening out now."

They waited for a full minute, but there was no acknowledgment of their call. Well, Harper told himself grimly, it's too late to start blaming each other now. Several times while they had been drifting above the mountains they had debated whether to call the global rescue service, but had decided against it, partly because there seemed no point in doing so while they were still airborne, partly because of the unavoidable publicity that would follow. It was easy to be wise after the event: who would have dreamed that they would land in one of the few places beyond Lifeguard's reach?

Dr. Elwin switched off the transceiver, and the only sound in the little tent was the faint moaning of the wind along the mountain walls within which they were doubly trapped-beyond escape, beyond communication.

"Don't worry," he said at last. "By morning, we'll think of a way out. There's nothing we can do until dawn-except make ourselves comfortable. So drink some of this hot soup."

Several hours later, the headache no longer bothered Harper. Though he suspected that a rib was indeed cracked, he had found a position that was comfortable as long as he did not move, and he felt almost at peace with the world.

He had passed through successive phases of despair, anger at Dr. Elwin, and self-recrimination at having become involved in such a crazy enterprise. Now he was calm again, though his mind, searching for ways of escape, was too active to allow sleep.

Outside the tent, the wind had almost died away, and the night was very still. It was no longer completely dark, for the Moon had risen. Though its direct rays would never reach them here, there must be some reflected light from the snows above. Harper could just make out a dim glow at the very threshold of vision, seeping through the translucent heat-retaining walls of the tent.

First of all, he told himself, they were in no immediate danger. The food would last for at least a week; there was plenty of snow that could be melted to provide water. In a day or two, if his rib behaved itself, they might be able to take off again-this time, he hoped, with happier results.

From not far away there came a curious, soft thud, which puzzled Harper until he realized that a mass of snow must have fallen somewhere. The night was now so extraordinarily quiet that he almost imagined he could hear his own heartbeat; every breath of his sleeping companion seemed unnaturally loud.

Curious, how the mind was distracted by trivialities! He turned his thoughts back to the problem of survival. Even if he was not fit enough to move, the Doctor could attempt the flight by himself. This was a case where one man would have just as good a chance of success as two.

There was another of those soft thuds, slightly louder this time. It was a little odd, Harper thought fleetingly, for snow to move in the cold stillness of the night. He hoped that there was no risk of a slide; having had no time for a clear view of their landing place, he could not assess the danger. He wondered if he should awaken the Doctor, who must have had a good look around before he erected the tent. Then, fatalistically, he decided against it; if there was an impending avalanche, it was not likely that they could do much to escape.

Back to problem number one. Here was an interesting solution well worth considering. They could attach the transceiver to one of the Lewies and send the whole thing aloft. The signal would be picked up as soon as the unit left the canyon, and Lifeguard would find them within a few hours-or, at the very most, a few days.

Of course, it would mean sacrificing one of the Lewies, and if nothing came of it, they would be in an even worse plight. But all the same . . .

What was that? This was no soft thudding of loose snow. It was a faint but unmistakable "click," as of one pebble knocking against another. And pebbles did not move themselves.

You're imagining things. Harper told himself. The idea of anyone, or anything, moving around one of the high Himalayan passes in the middle of the night was completely ridiculous. But his throat became suddenly dry, and he felt the flesh crawl at the back of his neck. He had heard something, and it was impossible to argue it away.

Damn the Doctor's breathing; it was so noisy that it was hard to focus on any sounds from outside. Did this mean that Dr. Elwin, fast asleep though he was, had also been alerted by his ever-watchful subconscious? He was being fanciful again....

Click.

Perhaps it was a little closer. It certainly came from a different direction. It was almost as if something-moving with uncanny but not complete silence-was slowly circling the tent. This was the moment when George Harper devoutly wished he had never heard of the Abominable Snowman. It was true that he knew little enough about it, but that little was far too much. He remembered that the Yeti, as the Nepalese called it, had been a persistent Himalayan myth for more than a hundred years.

A dangerous monster larger than a man, it had never been captured, photographed, or even described by reputable witnesses. Most Westerners were quite certain that it was pure fantasy, and were totally unconvinced by the scanty evidence of tracks in the snow, or patches of skin preserved in obscure monasteries. The mountain tribesmen knew better. And now Harper was afraid that they were right.

Then, when nothing more happened for long seconds, his fears began slowly to dissolve. Perhaps his overwrought imagination had been playing tricks; in the circumstances, that would hardly be surprising. With a deliberate and determined effort of will, he turned his thoughts once more toward the problem of rescue. He was making fair progress when something bumped into the tent.

Only the fact that his throat muscles were paralyzed from sheer fright prevented him from yelling. He was utterly unable to move. Then, in the darkness beside him, he heard Dr. Elwin begin to stir sleepily.

"What is it?" muttered the scientist. "Are you all right?"

Harper felt his companion turn over and knew that he was groping for the flashlight. He wanted to whisper: "For God's sake, keep quiet!" but no words could escape his parched lips. There was a click, and the beam of the flashlight formed a brilliant circle on the wall of the tent.

That wall was now bowed in toward them as if a heavy weight was resting upon it. And in the center of the bulge was a completely unmistakable pattern: the imprint of a distorted hand or claw. It was only about two feet from the ground; whatever was outside seemed to be kneeling, as it fumbled at the fabric of the tent.

The light must have disturbed it, for the imprint abruptly vanished, and the tent wall sprang flat once more. There was a low, snarling growl; then, for a long time, silence.

Harper found that he was breathing again. At any moment he had expected the tent to tear open, and some unimaginable horror to come rushing in upon them. Instead, almost anticlimactically, there was only a faint and far-off wailing from a transient gust of wind in the mountains high above. He felt himself shivering uncontrollably; it had nothing to do with the temperature, for it was comfortably warm in their little insulated world.

Then there came a familiar-indeed, almost friendly sound.

It was the metallic ring of an empty can striking on stone, and it somehow relaxed the tension a little. For the first time, Harper found himself able to speak, or at least to whisper.

"It's found our food containers. Perhaps it'll go away now."

Almost as if in reply, there was a low snarl that seemed to convey anger and disappointment, then the sound of a blow, and the clatter of cans rolling away into the darkness. Harper suddenly remembered that all the food was here in the tent; only the discarded empties were outside. That was not a cheerful thought. He wished that, like superstitious tribesmen, they had left an offering for whatever gods or demons the mountains could conjure forth.

What happened next was so sudden, so utterly unexpected, that it was all over before he had time to react. There was a scuffling sound, as of something being banged against rock; then a familiar electric whine; then a startled grunt.

And then, a heart-stopping scream of rage and frustration that turned swiftly to sheer terror and began to dwindle away at ever-increasing speed, up, up, into the empty sky.

The fading sound triggered the one appropriate memory in Harper's mind. Once he had seen an early-twentieth-century movie on the history of flight, and it had contained a ghastly sequence showing a dirigible launching. Some of the ground crew had hung on to the mooring lines just a few seconds too long, and the airship had dragged them up into the sky, dangling helplessly beneath it. Then, one by one, they had lost their hold and dropped back to the earth.

Harper waited for a distant thud, but it never came. Then he realized that the Doctor was saying, over and over again: "I left the two units tied together. I left the two units tied together." He was still in too much of a state of shock for even that information to worry him. Instead, all he felt was a detached and admirably scientific sense of disappointment.

Now he would never know what it was that had been prowling around their tent, in the lonely hours before the Himalayan dawn. One of the mountain rescue helicopters, flown by a skeptical Sikh who still wondered if the whole thing was an elaborate joke, came nosing down the canyon in the late afternoon. By the time the machine had landed in a flurry of snow, Dr. Elwin was already waving frantically with one arm and supporting himself on the tent framework with the other.

As he recognized the crippled scientist, the helicopter pilot felt a sensation of almost superstitious awe. So the report must be true; there was no other way in which Elwin could possibly have reached this place. And that meant that everything flying in and above the skies of Earth was, from this moment, as obsolete as an ox-cart.

"Thank God you found us," said the Doctor, with heartfelt gratitude. "How did you get here so quickly?"

"You can thank the radar tracking networks, and the telescopes in the orbital met stations. We'd have been here earlier, but at first we thought it was all a hoax."

"I don't understand."

"What would you have said, Doctor, if someone reported a very dead Himalayan snow leopard mixed up in a tangle of straps and boxes-and holding constant altitude at ninety thousand feet?" Inside the tent, George Harper started to laugh, despite the pain it caused. The Doctor put his head through the flap and asked anxiously: "What's the matter?"

"Nothing-ouch. But I was wondering how we are going to get the poor beast down, before it's a menace to navigation."

"Oh, someone will have to go up with another Lewy and press the buttons. Maybe we should have a radio control on all units...."

Dr. Elwin's voice faded out in mid-sentence. Already he was far away, lost in dreams that would change the face of many worlds. In a little while he would come down from the mountains, a later Moses bearing the laws of a new civilization. For he would give back to all mankind the freedom lost so long ago, when the first amphibians left their weightless home beneath the waves. The billion-year battle against the force of gravity was over.