Rick joined Zircon and Scotty at the bottom of the steps. Chahda was right behind him. The stairs ended in a long, low passage, just high and wide enough for a man to pass. It was perhaps fifty feet long, and it ended in blackness that indicated a bigger passage, or another cave, beyond. Rick touched the walls and noted the marks of ancient chisels. The passage had been cut in the living rock. "Have your rifles ready," Zircon directed. "Chahda, you have the big light. Lead the way and we'll cover you." Chahda switched on his big light and took the lead. The others, rifles ready for instant use, followed close behind. Big Zircon held his weapon over Chahda's shoulder as the Hindu boy walked slowly down the passage. In a moment they were at the entrance to the next passage or cave. Chahda peered in, turning his light from side to side. Zircon, looking over his head, said, "A large cave beyond. Very large. Chahda, do you see anything?" Chahda shook his head. "Only rock. Nothing inside I can see." "All right. Go ahead." The Hindu boy stepped into the cave, the rest following. Rick saw that Zircon hadn't exaggerated. The cave was even larger than the one that held the Black Buddha. Chahda's big light picked out the opposite wall dimly. The scientist brought his own light into play, turning it on the walls nearest them. "Odd," he muttered. "The character of the rock changes completely. This is almost surely limestone." Rick had to grin. Even chasing Long Shadow through an underground cavern couldn't quiet Zircon's scientific curiosity. "What do we do now, professor?" he asked. Zircon looked up from his examination of the whitish rock. "Eh? Oh. Sorry, Rick. Why, I suppose we explore a bit more. I don't think we'd better go far, however. Now that we know that Long Shadow is here, we had better return to camp and get extra food, batteries, and ammunition. However, I would like a look at the opposite side. There must be further passages, because this cave obviously doesn't contain our friend." "Suppose...." Scotty started to say. Rick never found out what Scotty was going to say, for at that moment the four whirled as something grated behind them. They were in time to see metal rods slam home across the entrance through which they had come! Rick and Scotty reached the entrance first. Each of the boys grabbed one of the rods and tugged. They were rigid. "We're locked in!" Rick's voice was harsh. "Let me look," Zircon said quietly. The boys stood back while he made a careful inspection. From floor to top of the passage entrance the metal bars blocked the way. They were about an inch thick, spaced only six inches apart. They had shot out of holes in one side of the passage and lodged in corresponding holes on the opposite side. None of them had noticed the holes. They had been too curious about what lay beyond the passage.