Richard Verner leaned back in his office chair with the alert look of a big cat as, across the desk, Nathan Bancroft, a quietly dressed man of average height, spoke earnestly.
"Last Saturday, Mr. Verner, a technician at one of our most highly classified research laboratories got away with the plans for a new and secret type of laser device. The scientist who invented the device evidently tried to stop him, and was stabbed to death."
Verner nodded intently.
Bancroft went on. "To understand the situation that's come about, you have to know that the region around this laboratory has a great many caverns. These are connected in a gigantic system of natural tunnels, rooms, crevices, and underground streams that have never been thoroughly mapped or explored.
"The technologist who stole the plans is an ardent speleologist—cave explorer. Possibly one reason for his hobby is that he suffers from hay fever, and cavern air is pure. In any case, over a period of years he's spent entire days in an underground complex of branching tunnels known as the Maze of Minos. A number of cave explorers have been lost in there, and the local people shun it. The only known expert on this underground maze is the murderer himself.
"Now, there's no question, Mr. Verner, but that this spy expected to be far away before the theft of the plans was discovered. But, by sheer good luck, the director of the laboratory discovered what had happened, and immediately notified the police. The police were lucky too—they spotted the technician's car just after the call came in. But then we all ran out of luck. The technician, taking the plans with him, escaped into this cavern—this Maze of Minos."
"And got away?" said Verner.
"Got clean away," said Bancroft. "The tunnels branch off in all directions, and of course it's as dark in there as the blackest possible night. He simply vanished."
Verner nodded again. "He's still in there?"
Bancroft said glumly, "Yes, he's still in there. We have a great many men on the spot, doing nothing but watch the known exits. But there's always the chance that he'll find some new way out, or knows of one, and get away. Meanwhile, we desperately need those plans. With the inventor dead, there are certain details we can clear up only from those papers. Yet, if we should get close, he just might take it into his head to destroy them. What we want to do is get to him before he realizes we're near. But how? How do we even find him in there?"
"Is he starving?"
"Not likely. He probably has caches of food for his longer explorations. And there's water in the caverns, if you know where to look."
"You want to get him alive, and by surprise?"
"Exactly."
"But he knows you're hunting for him in the cavern?"
"Oh, yes. We've brought in lights, and before we realized what we were up against, we set up loudspeakers and warned him to give up, or we'd come in after him. If he understood what we were saying over all the echoes, this must have amused him immensely. We could put our whole organization in there and get nothing out of a grand-scale search but sore feet, chills, and a dozen men lost in the winding passages. The thing is a standoff, and he knows it."
Verner asked thoughtfully, "And what brings you to me?"
Bancroft smiled. "We've consulted cave explorers, geologists, and all kinds of specialists without finding what we want. Then one of our men, who knows General Granger, remembered his saying he'd been helped in that mess at the hunting lodge by a 'heuristician.' We got in touch with Granger, who recommended you highly. We didn't know exactly what a 'heuristician' was—but we're prepared to try anything."
Verner laughed. "A heuristician is a professional problem solver. I work on the assumption that nearly all problems can be solved by the same basic technique, combined with expert knowledge. Some of my cases are scientific, some involve business situations, and others are purely personal problems. The details vary, but the basic technique remains the same. If the case interests me enough to take it in the first place, and if the necessary expert help is available, I can usually solve any problem—though sometimes there's an unavoidable element of luck and uncertainty."
"Well," said Bancroft, "we have plenty of experts on hand—all kinds. And I hope this problem offers enough of a challenge to interest you."
Verner nodded. "And we'd better lose no time getting there."
Many cars and several big trucks were parked outside the main cavern entrance. From outside, electric cables coiled into the brilliantly lighted mouth of the cavern, and there was a steady throb of engines as Verner and Bancroft walked in.
"Generators," said Bancroft. "We're trying to light this end as brightly as possible, and extend the lights inward. But it's a hopeless job. I'll show you why."
They pushed past a small crowd of men, who nodded to Bancroft and glanced at Verner curiously, and then they were in a brightly lighted chamber in the rock, about forty feet long by ten high, and twelve to fourteen feet wide. Here their voices and footsteps echoed as Bancroft led the way toward the far end, where a faint breeze of cool air blew in their faces.
"So far, so good," said Bancroft, stepping around a tangle of cables and walking through a narrow doorway cut in the rock. "But here we begin to run into trouble."
He stepped back to show a long brightly lit chamber where fantastic frieze-like shapes dipped from the ceiling to meet fairy castles and miniature ranges of mountains rising from the floor. Here the electric cables that lay along the floor fanned out in all directions, to wind around huge pointed cones into the well-lighted distance.
Wherever Verner looked, the stalactites and stalagmites rose and dipped endlessly, with new chambers opening out in different directions, and as Bancroft led the way, they clambered over the uneven slanting floor past waterfalls of rock, through little grottoes, and by shapes like thrones, statues, and weird creatures from fairyland.
For a long time they walked in silence except for the echoes of their own footsteps. Then suddenly it was dark ahead. The last giant electric bulb lit the shapes of stalagmites rising, one behind the other, till the farthest ones were lost in impenetrable shadows.
A gentle breeze was still in their faces—cool, refreshing, and pure. Somewhere ahead they could hear a faint trickling of water.
"Here," said Bancroft, "we come to the end of our string. These tunnels branch, then open out into rooms, and the rooms have galleries leading off from them, and out of these galleries there are still more tunnels. They twist, wind, and occasionally they even rejoin."
His voice echoed as he talked, and he pointed off to the right. "Over there, somewhere—I think that's the direction—there's an eighty-foot sheer drop with a little stream at the bottom, and from the wall of this drop other tunnels open out in various directions and on different levels. There are eyeless fish in the stream, and a kind of blind salamander—very interesting, but our problem is the complex of all those tunnels. A man who knew where he was going could pick the one tunnel he wanted out of a dozen or so at any given place. But we have to follow them all. And every so often they divide again or—look up there."
Bancroft pointed to a dark opening above a slope like a frozen waterfall.
"Probably that's another one. This whole place is honeycombed, filled with diverging and connecting tunnels. It's like trying to track down someone inside a man-size termite's nest. We thought he might have left some trace, some sign of where he'd gone. We thought we could follow him with dogs. We forgot that he's practically lived in here during his spare time ever since the laboratory was set up.
"There's a superabundance of clues. Dogs have followed one track through the dark right over the edge of a sudden drop, and been killed. We can find signs that he's been just about anywhere we look. We found a pair of sneakers at one place, and a cache of food at another." Bancroft shook his head. "Let's go out. There are some people you'll want to meet, now that you've seen what it's like in here, what our problem is."
Outside, in the warm fall night, a group of men quickly gathered around Verner and Bancroft.
One, an old man in dungarees and checked shirt, was well known locally as a cave explorer. A tall man in gray business suit was the director of the government laboratory, and he repeatedly sneezed and blew his nose. A boy in dungarees and old leather jacket told how he had seen the murderer-spy enter the cave, after crossing a nearby field; he was sure it was the man they were looking for.
"Heck, we all knew him. We'd often see him go in here. He knows more about these caves than anyone—well, except maybe Gramps Peters here."
The old man laughed. "Don't fool yourself. I know old Minotaur, at the other end of this, like I know the back of my hand. But this Maze—I admit I don't know it. I was in here maybe ten years ago, got lost, wandered around for five days, drinking the water in an underground stream, and finally made my way out of a collapsed sinkhole miles away from here. That was the end of the Maze for me. Now, this man you're looking for is a different animal. He's as good as lived in there."
The laboratory director sneezed and blew his nose again. "One reason he spent so much time there, especially in the fall, was the pure air of the caverns. He was, if anything, even more allergic than I am. He once told me that the only place an active man could find recreation out of doors in the fall, if he suffered from hay fever, was inside a cave."
Bancroft said, "We're watching all the known exits. We've sent teams of men through those tunnels, and we've only begun to grasp the difficulties. Somehow, we've got to locate him—but how?"
Verner glanced at the old man. "There seems to be a slight, steady current of air in there. That doesn't come from the outside, does it?"
"Gramps" Peters shook his head. "These passages are complicated, but in this part of the cavern most of the passages slope a little uphill. Up at the other end is what they call the Minotaur. There's an underground riverbed there; no river—that's eaten its way farther down—but there's this gentle flow of cold air. I suppose the air comes from the outside somewhere, maybe from hundreds of miles away, but you wouldn't know it by the time it gets here. It seems to flow into the Minotaur, and then branch out through the Maze. It's always fresh and cool. If you get turned around in a passage, that gentle breeze, when you come to a narrow place, will tell you which way you're headed."
When Verner was finished asking questions, Bancroft took him aside.
"You see now what we're up against, Mr. Verner?"
"I suppose you've got infrared equipment?"
"Yes, and if we knew where he was, it might help us find our way to him in the dark without warning him. But it won't help to send teams of men prospecting at random through all those tunnels. The last time we tried it we found nothing, and three men were seriously injured when they came to a sudden slope." He looked at Verner tensely. "Do you have any suggestion, any idea at all?"
Verner nodded. "If we're lucky. and if what we've been told is true, we may have him out of there in a few hours."
"If you can do that, you're a miracle worker."
"No miracle at all—just common sense. But this is a case where we'll need a little luck, But we'll have to work from the upper end—from the Minotaur."
The passages of the Minotaur were larger and looked less complicated than those in the Maze. Here the gentle current of cool air seemed stronger, steadier, and could sometimes be felt even in comparatively wide passages.
Verner and Bancroft waited tensely, and then down the passage ahead came a small group, carrying a struggling man who was swearing violently.
"Find him?" said one of his captors, grinning. "All we had to do was follow the sounds he was making. He was sitting by a cache of food that would have lasted a week, with the plans still in his pocket."
Bancroft was looking at Verner, but he didn't speak. An awful choking and strangling from the prisoner made Bancroft turn in amazement. The choking and strangling noises were interspersed with violent sneezing.
Down the passage the men had stopped thrashing the stacks of ragweed, which had sent thick clouds of pollen drifting through the passage and into the Maze. The pollen had unerringly found its target—the murderer-thief who suffered from hay fever.