They started to retrace their tracks. Partly down the wind tunnel they found the downward slope on which they had traveled before. Robin flashed his lamp down its steep pitch. He saw nothing. Gingerly he began to work his way cautiously down the sharp slope. Peter followed behind. Halfway down, Robin stopped for breath. When he caught it, he whispered, "I just thought of something. How do we know Von went down here? Maybe he's gone farther up the tunnel, waiting to slip back and get behind us." "I don't think so," said Peter. "I looked in the dust up along the tunnel for his footprints and saw none. He must be ahead of us." They slid on down the slope, found themselves at the beginning of the upper series of connected broken bubbles. Along this they trekked, passing along the debris-strewn floor, picking their way carefully. Shining their lamps ahead as they went, they saw no sign of motion. Finally they came to the hole in the floor, through which they would have to drop several feet into the cave below. Robin switched off his light as they approached it, whispered to Peter to do the same. They stood silently in the pitch darkness. Then Robin nudged Peter, pointed with his hand against Peter's. The hole in the floor was faintly visible. There was a dim flickering coming from it. Robin whispered, "It must be Von's flashlamp. He's down there, waiting for us." Peter nodded in the darkness. "It was the logical spot. He probably hopes to shoot us as we drop through the hole." The two stepped carefully up to the hole, not yet using their lights. They kneeled down, looked. The cave below was almost dark. But from just outside it, from the tunnel that led into it, was a flickering light. Their crazed enemy was lurking there, waiting. "What do we do now?" muttered Peter. Robin looked carefully. "I think I have it. Untie the cord and give it to me." Peter untied his end of the nylon rope that linked them. Robin undid his end, took his flashlamp, tied it to the cord. He whispered his plan to Peter. Robin lit the flash, backed away from the hole several feet, and then kicked some rocks and began to make a clattering noise. At the same time he began to talk loudly, as if conversing with Peter. Meanwhile, Peter was crouched at the edge of the hole, his Tokarev automatic firmly wedged against one side of the hole while it was pointing directly at the faint spot of light below which Von Borck was hiding. Robin reached the hole, making sure he was creating enough noise for the rocket pilot to hear him. Then he waved his lamp a few times, flickering it around the cave below, and kneeling down, began to lower it on the cord, trying to keep its beam pointed at the tunnel in which their foe waited. This was the bait on their trap.