Somewhere, perhaps, beyond the Lake of Darkness, was Long Shadow.

Rick felt certain of it. The Tibetan who lay unconscious at his feet had been going somewhere. He had walked steadily and purposefully, with some definite destination in mind. What was more logical than to assume that the Tibetan had been heading for the hidden plant where heavy water was being produced?

Once the plant was found, Long Shadow would be found there, also. Even if he were not there at the moment, he would come. And when he did, Rick intended to do something about it. He had no definite plans. He only knew that somehow he would force Long Shadow to unlock the gate to the outer world.

His oars dipped rhythmically as he pulled out into the lake. The infrared light was directed toward a jutting edge of limestone on the shore he had just left. He was using the rock formation as a marker so he could steer a straight course.

He wondered about his friends. Were they lost, too? Or had they managed to keep to the right trail by following the tiny drops of candle wax? The odd tin candleholder explained why there wasn’t more wax to follow. The holder caught most, but not all of the drippings.

The rocky shore of the underground lake receded rapidly. Rick stopped rowing and turned, switching the infrared light toward the direction in which he was heading. He could see the opposite shore now, but dimly. Knowing that the infrared light was effective at eight hundred yards, he estimated the lake to be about twelve hundred yards wide. That was over three-fifths of a mile.

When he shot the light up and down the lake, he saw nothing but the black water. That meant the lake was more than sixteen hundred yards long. He turned the light upward and surveyed the ceiling. It was irregular, varying in height from a dozen feet to over two hundred. In one place, the ceiling came down to within a few feet of the black water.

It was an eerie place. Rick’s quick imagination turned him into the mythical Charon, who ferried the dead across the River Styx into Hades. He grinned mirthlessly. The limp figure of the Tibetan gave substance to the picture.

He bent over the man, reaching for his wrist. The pulse was weak but steady. He had given the Tibetan a healthy belt. There was no sign of returning consciousness. But Rick wasn’t worried. If he had hurt the man badly, the pulse would have been thready and unsteady. He would wake up presently, and his head would feel like a pillow stuffed with rocks, but otherwise he would be all right. Rick knew. He had been knocked out himself a couple of times.

He resumed rowing, and his steady strokes brought him closer to the opposite shore. He turned to examine it and saw that a rocky ledge rose gradually out of the water. In a short time he felt the boat grind against the limestone.

He got out and pulled the craft up on the shore, which was worn smooth by the water. The ledge varied from ten to fifty feet in width. Beyond it, the roof of the cavern came down sharply to form a curving wall broken in countless places. He could see into the broken places nearest him. They were the beginnings of more cave labyrinths.

Now that he had reached the opposite shore, what was he to do? Again he leaned over the Tibetan. The man showed no signs of returning consciousness.

Rick cast his invisible light up and down the shore. Nothing indicated that humans ever had been there before him. He realized that the wisest thing would be to wait until his guide returned to consciousness and then force him to lead the way once more. But he was impatient. Somewhere along the shore there must be signs he could follow.

He pulled the boat up as high as he could, then used strips torn from the Tibetan’s own clothes to bind and gag him. That done, he picked up the infrared camera and his rifle and stood a moment in indecision. Which way?

It was a tossup. Finally he decided to keep going in the general direction the Tibetan had led him. He paused long enough to inspect his rifle. After firing, he had failed to lever another cartridge into the chamber. He did so now, then put the hammer on half cock so it couldn’t fire accidentally, and started off.

It was easy going in most places. But now and then he came to a point where the shore ledge narrowed and he had to crawl. Once he skirted an outcropping by walking in the water, feeling his way carefully so he wouldn’t step off a ledge into the depths.

After a while he began to think he hadn’t been very smart. He was getting exactly nowhere. As far ahead as the infrared beam could penetrate, there was nothing but the curving shore. In some places the lake narrowed to a channel less than a hundred feet wide, then it broadened again until he could no longer see the opposite shore. He couldn’t guess how far he had walked from the boat. He thought it must be at least a quarter mile.

Presently he found a place where a limestone pillar made a comfortable back rest and sat down. He switched off the infrared light, and instantly all light was blotted out. It was startling, even more so than when he had switched off the flashlight, because the infrared beam gave the illusion of a sort of gray daylight.

He sat quietly, waiting for some of the weariness to leave his legs, his eyes closed. After a while he opened them again, more from habit than with the intention of seeing anything. He couldn’t see even the tip of his nose it was so dark. Then suddenly he realized it wasn’t as dark as he had expected!

There was a faint luminous quality that outlined the shore of the lake. He studied the line of demarkation, then guessed that the faint luminosity must come from microscopic plant or animal life that clung to the rock underwater. Sea water had a phosphorescence sometimes for the same reason.

His eyes followed the faint line up the shore in the direction he had been traveling. The silver phosphorescence turned a faint yellow. Almost out of the range of his vision the yellow was picked up by the water, like the dimmest moonlight.

He studied it for long minutes, trying to figure out the reason for the phenomenon, then he almost leaped out of his skin. The water was reflecting the yellow light! It didn’t come from the water the way the luminous silver did!

He got to his feet. Reflection meant man-made light!

It was hard to follow the faint yellow light. When he switched on the infrared, the light vanished completely. When the infrared was off, he couldn’t find his way.

He compromised, going a hundred feet or so with the infrared on, then turning it off and sitting quietly until his eyes adjusted themselves and he could see the yellow glow once more. After he did this a few times he could see that the light was growing slightly stronger.

Then, as he progressed, he realized why he couldn’t see the source of the light. It was around a corner of the rock wall.

After several minutes of alternate walking and waiting he reached the corner. It dropped sharply into the water, and when he flashed the infrared down, he saw that the water was black. No shelf here to walk on. He debated for a moment. He could swim around, or he could try to find another way. There were plenty of cave openings. One of them might go through.

He had been lost once, and he didn’t intend to let that happen again. He tore open the packet of emergency rations he had brought, searching for something with which to lay a trail.

Inside the waxed container were little cans of food and a packet of hard crackers. The crackers would do.

But looking at the food reminded him that he hadn’t eaten in a long time. He didn’t know if it was hours, or days. He had lost all track of time. He took the can key and unwound the narrow sealing strip on a container of cheese. It tasted wonderful. He devoured every bit of it, including the crumbs left in the can. Then he opened a can of meat and ate that, too. He had been sipping at his canteen at various times, but it was still more than half full. He detached the canteen cup and filled it from the lake, tasting it cautiously. The water had a flat taste, like boiled water, but it was all right. He drank deeply, then filled the canteen.

His hunger and thirst satisfied, he surveyed the various openings around him, then chose the one nearest the corner he wished to get around. At the very entrance, he placed the empty cheese tin. Inside the cave, he turned to be sure it was clearly visible, then walked across to an opening that seemed likely to lead him in the right direction. He placed the second can at that opening and went into the passage formed by a series of stalagmite columns. It was a dead end. He returned to the cave where he had left the cans, picked up the empty meat can, and tried another entry.

He was completely calm now. He knew that humans, even though enemies, were not far away. And he was quite sure that his friends were all right. They would take steps to leave a trail so they would not get lost as he had done.

The second passage was better. He wound in and out through the limestone formations, leaving a trail of broken cracker crumbs. Every now and then he turned to see that the trail was plain. He grinned. Hadn’t he read a story when he was a kid about some children who had left a trail of crumbs only to have the birds eat them?

No danger of that here. No self-respecting bird would get near the place.

It wasn’t long before he ran out of crumbs. Then he tore his handkerchief into tiny bits and used that. When he reached the end of the cloth scraps, he sat down to rest, turning off the infrared light while he carefully shredded a big piece of his shirttail.

As his eyes adjusted themselves to the darkness, he saw the yellow light again, only stronger this time! Carefully, his heart beating excitedly, he turned the infrared light in the direction of the yellow glow and switched it on. Before him was a big opening in the limestone. He surveyed the floor carefully and saw that there was nothing over which to trip. He turned off the infrared light, and, leaving a trail of torn cloth behind him, he crawled toward the source of the light.

He came out on the shore of the lake once more. Before him stretched the black water, the yellow light dancing across its surface. And the source of the light was not from candles, but from torches!

Across the water, perhaps a hundred yards away, a half dozen torches burned, their light lost in the emptiness of the great lake cave. Near the torches he could see figures moving and knew with sudden relief that he had found the enemy camp.

He turned on the infrared light, aiming it at the torches, and through his special glasses he saw the scene light up.

Where the torches blazed was a great shelf of rock, stretching back several hundred feet to where the rock wall began once more. On the shelf were a dozen men, sitting around a tiny cooking fire much paler than the torches themselves. They were Tibetans, like the one he had captured.

He saw an odd structure at the water line and after a little study realized that it was a barge of some kind, perhaps a floating pier. It had odd derricklike wooden ladders on it. There were four of them, perhaps three feet high. Beyond the barge he made out at least two flat-bottomed boats.

Further back, against the limestone wall, he could see tents or lean-tos made of some kind of cloth. He couldn’t see clearly, but thought the cloth might be felt. This, then, was a permanent camp! The tents must be there to offer some protection against the cold and dampness.

He inspected the men again. They were all short. None of them could be Long Shadow.

“Now what?” Rick asked himself.

It was certain that Long Shadow would come to the camp sooner or later. It was almost as certain that Scotty, Zircon, and Chahda, if they followed the trail of the wax candles carefully, would arrive sooner or later at the boat landing to which the Tibetan had led him. Always provided they hadn’t been ambushed. He shivered at the thought. The cave formations would make it easy for the enemy to lie in wait. Then, even with their old-fashioned muskets and lack of shooting ability, they could pick off the little party.

But they wouldn’t do it without cost! Scotty was deadly with a rifle. Zircon was a better than average shot.

Rick debated. It was no good to make his presence known. Far better to lie in wait until Long Shadow came. Then, if he could take the camp by surprise, his rifle would do the rest for him.

But how to take it by surprise?

He scanned the shore around the camp. In several places between him and the camp shelf, the rock wall came right down to the lake’s edge. Unless he wanted to search for a way through the caves, he would have to swim. Or use a boat.

Beyond the last sheer place, the camp shelf started. Its edge curved and twisted for a little distance. If he could get to the starting point, he could keep undercover easily enough. Then, making his way along the wall, he could probably escape being seen until he was almost at the tents. With luck, a sudden dash would bring him right to the enemy without being seen first.

That was how he would do it. He would go back and get the boat, then lie in wait in this very place until the time came. He withdrew from the entrance, then paused suddenly. The men around the fire were getting to their feet and walking toward the water. He watched as they peered into the darkness in the direction he thought of as “down lake.” One of them ran to a torch, pulled it out of its holder, ran back to the water’s edge, and waved it.

A signal! To whom?

Two of the men were kneeling just beyond the barge, and a moment later they proceeded to get into the two flat-bottomed boats he had seen. What they had been doing was untying the boats. He watched as they rowed out onto the black lake.

They must be going after someone!

Rick hurried back the way he had come, following the path of torn cloth, then the broken cracker crumbs. He would have to hurry. The Tibetans might have gone after Long Shadow!

He retraced his steps at a pace that was half-walking, half-running. The trail he had left showed clearly in the infrared light. In a few moments he came out of the caves onto the lake shore once more, and he saw the signal that had summoned the boats. A red light was now clearly visible. He thought it was right at the point from which he had pushed off in the Tibetan’s boat.

A sudden thought struck him. Wouldn’t they miss the Tibetan and the boat? He hurried faster. Now and then he stopped to listen, and he could hear the sound of oars in the water.

It didn’t take long to reach his boat. When he leaned over the Tibetan, frightened black eyes peered up at him. He tested the man’s bonds. They were tight enough to be effective, but not so tight they cut off his circulation. He knew the gag was uncomfortable, but he didn’t dare remove it. As assurance that he meant no harm, he patted the man on the shoulder. Some of the wild fright went out of the beady eyes.

Working quietly, Rick pushed the boat out into the water. He wasn’t afraid of being seen. Candles or torches didn’t cast enough light to penetrate the blackness as the infrared beam did. But he might be heard. He had to be as quiet as possible.

He used only one oar, kneeling in the stern and paddling the flat-bottomed craft like a canoe. The infrared camera, placed on the seat with the beam directed ahead of him, gave him plenty of light to see. Once in a while he turned the beam around. The two boats were making good progress toward the red signal. The beam of the infrared camera didn’t penetrate far enough for him to see what or who was under the red light.

He rounded the corner that had blocked his way and paddled silently along the rocky wall. The two boats were out of sight now.

Rounding the corner gave him a clear view of the torches, but he knew the men around them couldn’t see him.

The way was longer than he had thought. He paddled in and out of coves, past grottoes in the rocky wall. Then, at last, he saw the little pile of torn cloth he had left on the shore at the end of his cave trail. He had put all the cloth not needed for marking trail in one place, not because he had been foresighted, but because he hadn’t needed it any more. He was glad now of the accident that marked the right place, otherwise he couldn’t have identified it from the rest of the openings in the wall.

He pulled the boat up to it and anchored it by the rope to a convenient stalagmite. Then he half-lifted, half-dragged the trussed Tibetan into the cave and out of sight of the lake.

Rick searched the water for some sign of the boats, and thought he heard them coming. He went back to the Tibetan, took his canteen, unscrewed the top, and placed it on the rock. Then, kneeling over his captive, he took the man’s throat in one hand. With the other he undid the rag that held the gag in place. Pressure of his fingers warned the Tibetan he would be strangled if he so much as squeaked. Then Rick pulled the torn rags he had used as a gag from the man’s mouth, lifted him to a sitting position, and held the canteen to his lips with his free hand.

The Tibetan drank greedily. Rick let him rest for a moment, then held the canteen again. The man drank his fill, then nodded his thanks. Rick quickly replaced the gag and bound it in place, then used another piece of cloth torn from the man’s clothing to lash one leg to a stalagmite. He didn’t want to risk having the man wriggle to the entrance at the wrong time, and sound an alarm.

Rick was exultant. High excitement was rising in him, because he thought it was only a matter of time now before Long Shadow would come, even if his enemy was not already in one of the boats that were making their way back to the camp.

He switched out the infrared light, placing the camera on the ground, pointing toward the boat landing. Then he lay down on his stomach, rifle thrust out in front of him and handy to his hand. He could wait. He could wait days, if necessary. Because once Long Shadow came, he would force him to show the way to the outside, and he would force him to locate the others.

If Long Shadow refused to co-operate ... Rick’s lips tightened. Then at least he wouldn’t be lonesome in the Caves of Fear. His enemy would be his company until the end.