While Chahda and Scotty remained on sh.o.r.e, Zircon and Rick pushed the barge out into the lake. Rick got a Nansen bottle ready.

The bottle was made of metal, each end equipped with a spring cap. The bottle was lowered on a wire with the ends open, permitting water to flow through it freely. When it reached the desired depth, a metal weight called a "messenger" was attached to the wire and dropped. The weight of the messenger released devices that closed the caps, thus trapping the water sample inside. A bra.s.s spigot on the side permitted the sample to be taken out easily when the bottle was hauled up again.

They had brought four bottles from Long Shadow's stores. The first one was lowered to the very bottom, and it took a long time getting there.

The reel of wire with which the barge was equipped ran out and out until a full seven hundred feet of it had disappeared into the dark depths of the lake. Rick was glad the reel of wire had a geared handle. Pulling that weight up would be no fun.

Once the slackening of the wire told them that bottom had been reached, Zircon put the messenger on the wire and let it go. Seconds later, a tug on the wire told them it had struck and Rick reeled in.

Other samples were taken at five, ten, and fifteen feet from the bottom.

Zircon marked the bottles, then they paddled back to sh.o.r.e.

Long Shadow spoke up. "Of course you have testing equipment?"

"At our camp near Korse Lenken," Zircon a.s.sured him.

"You'll find what you expect," the Eurasian said.

"Thank you. And now, we'll also thank you to lead us out of here."

"No," Long Shadow said.

"You're beaten," Zircon said reasonably. "Why not admit it and co-operate? We've nothing against you even if there were law in Tibet.

See us to the outside and open the barred gate and you're at liberty to go."

Rick started to protest, then he realized Zircon was right. Law in this part of the world was the law of the rifle. There was nothing they could do to Long Shadow or Ko.

Long Shadow considered. "I suppose you're right. My little business deal is over, at least for the time being." He raised his voice and yelled in Tibetan.

The boys grabbed up their rifles as Tibetan heads showed from the caves, black eyes blinking in fear.

"They will carry me and Ko," Long Shadow said calmly. "Now let us be on our way." He smiled. "I must admit I have a selfish interest in all this worry about getting to the outside. This ankle is beginning to hurt, and I won't mind having one of the lamas with medical skill take a look at it."

"How about letting a Hong Kong police doctor take a look at it?" Rick asked. Long Shadow's cheerfulness was getting on his nerves. The man acted more like a guest than a prisoner.

"I don't think we need go that far," Long Shadow replied. "The lamas are quite capable."

"I wasn't concerned about your ankle," Rick corrected. "I was thinking that the Hong Kong police might like to get their hands on the kind of citizen who goes around shooting up hotels with a Schmeisser machine pistol."

Long Shadow stopped smiling abruptly. "You couldn't prove that," he said swiftly.

"Why not?" Scotty asked, "We'll let the police see if the slugs from your machine pistol don't match those in the hotel wall. By the way, where is the Schmeisser? I haven't seen it around."

Long Shadow recovered his grin. "You'll never see it again. I took the precaution of disposing of it, in case the police in the hotel area had been alerted. Don't bother to ask me how I got rid of it."

"We won't," Zircon replied. "Obviously, you wouldn't tell us. However, perhaps you will tell us how long it will take to get out of here?"

"About ten minutes."

At their evident surprise, Long Shadow added, "I should have said once we cross the lake it will take about ten minutes. You came a very long way around, you see. I realize you followed the candle droppings, but I'm afraid those were left some time ago, when I first explored the cave. The first entrance you tried was the correct one, even though you didn't suspect the presence of a door. When you took the open way, you approached by a very twisting path."

"Just to satisfy my curiosity," Scotty asked, "why did your men capture us, then bundle us into the boats and bring us here? And where were you all that time?"

Long Shadow shrugged. "I knew your guide and bearers were outside, at Korse Lenken, of course. My men have kept an eye on you. I also felt they probably would start a search after you failed to return. It was almost certain they would find the entrance to the caverns behind the Black Buddha, and, like you, they would probably follow the candle drippings. The drippings would lead them nowhere. Unless they found the secret door, there would be no chance of them finding you here in our permanent camp. Hence, I had you brought here. Ko and I were waiting in the cave I use for an office. When we thought time enough had elapsed for my orders to be carried out, we came here. Meanwhile, we took a nap.

Are you satisfied?"

"You never intended that we should see daylight again," Rick stated. He winked at his friends. "Suppose we tie a few stalact.i.tes to your feet, and Ko's, and see how long it takes for you to get down to where the heavy water is?" He looked meaningly at the lake.

Ko groaned, but Long Shadow only smiled. "If that's the way you want it," he said, "it will at least be quick. Both of us are done for, whether you know it or not. Your Mr. Bradley will see to that."

As Long Shadow had said, it was little more than ten minutes after crossing the lake before the party reached the cave under the Black Buddha. They had pa.s.sed through the cave where Rick had found the Tibetan. Again he realized how lucky he had been. Some good angel had led him to the main route. Had he fallen asleep in some other cave, he might still be wandering through the labyrinth.

The rifles taken from Scotty and Zircon by Long Shadow's men had been found in one of the tents. With Rick's rifle, they were insurance against treachery. But Long Shadow seemed resigned, for some reason Rick couldn't fathom, and Ko did nothing but curse the bearers who carried him.

Before reaching the great cave they stopped at a blank wall. At a signal from Long Shadow, one of the Tibetans reached behind a stalagmite and pulled a lever. A section of the wall swung open, disclosing the pa.s.sage they had thought stopped in a dead end.

In a few moments they were crossing the outer cave, and Rick saw at once that the bars across the entrance pa.s.sage were gone.

"When the inner door opens from the inside, the bars also open," Long Shadow said. "There is another cave under this one where the mechanism is located. No, I am not responsible. The ancient ones who made the Black Buddha also made the doors and the mechanism."

Rick ran ahead through the pa.s.sage. He found the leather thong that controlled the door and pulled. The metal tongue came out of its slot permitting the counterbalance to swing the trap door upward. The others were behind him with their lights, and Rick saw his shadow loom large on the wall behind the Black Buddha. In the same way, the Long Shadow had been projected upward, probably by the light from a candle in the hands of a Tibetan bearer. He experimented, backing down a few steps. His shadow seemed to fold downward into the oblong box of light cast by the flashlights. When he walked up the stairs again, the shadow grew out of the bottom of the projected oblong of light.

As Rick reached floor level, he froze suddenly, his finger slipping the hammer of his rifle to full c.o.c.k. There were lights in the cave! As he turned to call a warning, yellow-robed lamas, who had seen the reflected light on the rear wall, poured around the statue with wild yells, their torches held high.

"Something's up," Rick called to the others. "Watch it!"

Under the threat of Rick's rifle, then Scotty's and Zircon's, the lamas fell back until the group stood alongside the Black Buddha, looking into the cave. There were torches everywhere! And cooking fires. Rick's first thought was that they had returned in the midst of a religious celebration.

And then he saw Sing. The Chinese guide ran to them, his face split by a wide grin.

"You came," he exclaimed happily. "We were about to tear the mountain down, stone by stone! Where is the Indian boy?"

Chahda came from behind the statue, herding the Tibetans who carried Long Shadow, Ko, and the Nansen bottles. Sing turned and yelled.

The lamas broke into cries of approval at the sight of Chahda. Several of them ran to him and pressed his hand. He was a favorite, obviously.

"They came to help when I told them the Indian boy was in danger," Sing explained. "We were ready to start digging holes to find the caverns, because we couldn't find the door." He eyed Long Shadow curiously and grinned at the sight of Ko. "Should I get my frying pan again?" he asked.

"Might be a good idea," Rick said.

"My boss not come yet?" Chahda asked.

Sing clapped hands to his head in a gesture of self-annoyance. "I forgot. A letter came. One of the consulate guards, a Chinese who knows this part of the world, brought it from Chungking. It may be from Mr.

Bradley, because it came originally from Hong Kong."

Zircon took the envelope while Rick, Scotty, and Chahda looked over his shoulder. The envelope was marked for delivery from Hong Kong to Chungking via diplomatic pouch. It was addressed to Zircon, with the note, "Urgent. Forward by messenger." Bradley's initials were signed to it.

The scientist ripped the envelope open and, looking around to be sure Long Shadow and Ko were out of earshot, he read: