"This is evidently their landing place," whispered Dr. Bird. "The next thing to find is their hiding place."

He rose and started forward but sank at once to the ground and dragged Carnes down with him. On the hill which formed the opposite side of the hollow a line of light showed for an instant as though a door had been opened. The light disappeared and then reappeared, and as they watched it widened and against an illuminated background four men appeared, carrying a fifth. The door shut behind them and they made their way slowly toward the waiting globe. They laid down their burden and one of them turned a flash-light on the globe and opened a door in its side through which they hoisted their burden. They all entered the globe, the door closed and with a slight whirring sound it rose in the air and moved rapidly toward the northeast.

"That's the place we're looking for," muttered Dr. Bird. "We'll go around this hollow and look for it. Be careful where you step; they must have ventilation somewhere if their laboratory is underground."

Followed by the secret service operative, the doctor made his way along the edge of the hollow. They did not dare to show a light and it was slow work feeling their way forward, inch by inch. When they had reached a point above where the doctor thought the light had been he paused.

"There must be a ventilation shaft somewhere around here," he whispered, his mouth not an inch from Carnes' ear, "and we've got to find it. It would never do to try the door; if any of them are still here it is sure to be guarded. You go up the hill for five yards and I'll go down. Quarter back and forth on a two hundred yard front and work carefully. Don't fall in, whatever you do. We'll return to this point every time we pa.s.s it and report."

The operative nodded and walked a few yards up the hill and made his way slowly forward. He went a hundred yards as nearly as he could judge and then stepped five yards further up the hill and made his way back. As he pa.s.sed the starting point he approached and Dr. Bird's figure rose up.

"Any luck?" he whispered.

Dr. Bird shook his head.

"Well try further," he said. "I think it is probably beyond us, so suppose you go fifteen yards up and quarter the same as before."

Carnes nodded and stole silently away. Fifteen yards up the hill he went and then paused. He stood on the crest of the hill and before him was a steep, almost precipitous slope. He made his way along the edge for a few yards and then paused. Faintly he could detect a murmur of voices. Inch by inch he crept forward, going over the ground under foot. He paused and listened intently and decided that the sound must come from the slope beneath him. A glance at his watch told him that he had spent ten minutes on this trip and he made his way back to the meeting place.

Dr. Bird was waiting for him, and in a low whisper Carnes reported his discovery. The doctor went back with him and together they renewed the search. The slope of the hill was almost sheer and Carnes looked dubiously over the edge.

"I wish we had brought the parachutes," he whispered to the doctor.

"We could have taken the ropes off them and you could have lowered me over the edge."

Dr. Bird chuckled softly and tugged at his middle. Carnes watched him with astonishment in the dim light, but he understood when Dr. Bird thrust the end of a strong but light silk cord into his hands. He looped it under his arms and the doctor with whispered instructions, lowered him over the cliff. The doctor lowered him for a few feet and then stopped in response to a jerk on the free end. A moment later Carnes signaled to be drawn up and soon stood beside the doctor.

"That's the place all right," he whispered. "The whole cliff is covered with creepers and there is a tree growing right close to it.

If we can anchor the cord here, I think that we can slide down to a safe hold on the tree."

A tree stood near and the silk cord was soon fastened. Carnes disappeared over the cliff and in a few moments Dr. Bird slid down the cord to join him. He found the detective seated in the crotch of a tree only a few feet from the face of the cliff. From the cliff came a p.r.o.nounced murmur of voices. Dr. Bird drew in his breath in excitement and moved forward along the branch. He touched the stone and after a moment of searching he cautiously raised one corner of a painted canvas flap and peered into the cliff. He watched for a few seconds and then slid back and silently pulled Carnes toward him.

Together the two men made their way toward the cliff and Dr. Bird raised the corner of the flap and they peered into the hill. Before them was a cave fitted up as a cross between a laboratory and a hospital. Almost directly opposite them and at the left of a door in the farther wall was a ray machine of some sort. It was a puzzle to Carnes, and even Dr. Bird, although he could grasp the principle at a glance, was at a loss to divine its use. From a set of coils attached to a generator was connected a tube of the Crookes tube type with the rays from it gathered and thrown by a parabolic reflector onto the s.p.a.ce where a man's head would rest when he was seated in a white metal chair with rubber insulated feet, which stood beneath it. An operating table occupied the other side of the room while a gas cylinder and other common hospital apparatus stood around ready for use.

Seated at a table which occupied the center of the room were three men. The sound of their voices rose from an indistinct murmur to audibility as the flap was raised and the watchers could readily understand their words. Two of them sat with their faces toward the main entrance and the third man faced them. Carnes bit his lip as he looked at the man at the head of the table. He was twisted and misshapen in body, a grotesque dwarf with a hunched back, not over four feet in height. His ma.s.sive head, sunken between his hunched shoulders, showed a tremendous dome of cranium and a brow wider and even higher than Dr. Bird's. The rest of his face was lined and drawn as though by years of acute suffering. Sharp black eyes glared brightly from deep sunk caverns. The dwarf was entirely bald; even the bushy eyebrows which would be expected from his face, were missing.

"They ought to be getting back," said the dwarf sharply.

"If they get back at all," said one of the two figures facing him.

"What do you mean?" growled the dwarf, his eyes glittering ominously.

"They'll return all right; they know they'd better."

"They'll return if they can, but I tell you again, Slavatsky, I think it was a piece of foolishness to try to take two men in one night. We got Bird all right, but it is getting late for a second one, and they had to take Bird over a hundred miles and then go nearly three hundred more for Williams. The news about Bird may have been discovered and spread and others may be looking out for us. Carnes might have recovered."

"Didn't he get a full dose of lethane?"

"So Frick says, and Bird certainly had a full dose, but I can't help but feel uneasy. Our operations were going too nicely on schedule and you had to break it up and take on an extra case in the same night as a scheduled one. I tell you, I don't like it."

"I'm sorry that I did it, Carson, but only because the results were so poor. We had planned on Williams for a month and I wanted him. And Bird was so easy that I couldn't resist it."

"And what did you get? Not as much menthium as would have come from an ordinary bookkeeper."

"I'll admit that Bird is a grossly overrated man. He must have worked in sheer luck in his work in the past, for there was nothing in his brain to show it above average. We got barely enough menthium to replace what we used in capturing him."

"We ought to have taken Carnes and left Bird alone," snorted Carson.

"Even a wooden-headed detective ought to have given us a better supply than Bird yielded."

"We are bound to meet with disappointments once in a while. I had marked Bird down long ago as soon as I could get a chance at him."

"Well, you ran that show, Slavatsky, but I'll warn you that we aren't going to let you pull off another one like it. I take no more crazy chances, even on your orders."

The hunchback rose to his feet, his eyes glittering ominously.

"What do you mean, Carson?" he asked slowly, his hand slipping behind him as he spoke.

"Don't try any rough stuff, Slavatsky!" warned Carson sharply. "I can pull a tube as fast as you can, and I'll do it if I have to."

"Gentlemen, gentlemen!" protested the third man rising, "we are all too deep in this to quarrel. Sit down and let's talk this over. Carson is just worried."

"What is there to be worried about?" grunted the dwarf as he slid back into his chair. "Everything has gone nicely so far and no suspicion has been raised."

"Maybe it has and then again maybe it hasn't," growled Carson. "I think this Bird episode to-night looks bad. In the first place, it came too opportunely and too easily. In the second place Bird should have yielded more menthium, and in the third place, did you notice his hands? They weren't the type of hands to expect on a man of his type."

"Nonsense, they were acid stained."

"Acid stains can be put on. It may be all right, but I am worried.

While we are talking about this matter, there is another thing I want cleared up."

"What is it?"

"I think, Slavatsky, that you are holding out on us. You are getting more than your share of the menthium."

Again the dwarf leaped to his feet, but the peace-maker intervened.

"Carson has a right to look at the records, Slavatsky," he said. "I am satisfied, but I'd like to look at them, too. None of us have seen them for two months."

The dwarf glared at first one and then the other.