Just as he had expected, as the swinging lamp was about halfway down, dangling presumably in the helpless hand of a man being lowered to the floor--as Von Borck was supposed to think--the figure of the German appeared in the cave, uttering a wild yell of triumph and aiming a big pistol at the moving light. Two guns went off at the same instant. There were two flashes of fire, two deafening blasts of sound. Von Borck's bullet shattered the swinging flashlamp, blew it into a dozen fragments. Peter's bullet struck Von Borck in the chest, hurling him against the wall to fall in a heap on the floor. Without wasting time, Peter simply stepped into the hole and drifted downward in the low force of Moon gravity. Robin followed suit. They leaned over the German's body. Robin looked at the pale, mustached face, the staring eyes. "I think he's dead," he said. "Though he could be only unconscious." He reached over, started to feel the man's face to find out whether he still breathed. "Look out!" shouted Peter suddenly and grabbed Robin, pulling him to one side. Robin looked up and back. Above him, with maddening leisureliness, the entire ceiling of the underground bubble was dropping down, dropping in several giant chunks, several Earth tons of rock falling toward them. With a mad scramble the two leaped to safety in the tunnel leading downward. There was a slow grinding crash as the shattered roof of the cave settled to the floor, crushing the body beneath it, blocking and sealing the tunnel. "Come on!" Peter grabbed Robin's arm. "The rest of it is caving in! We'd better run!" They dashed down the tunnel, as it crashed behind them. On they ran, following the twisted trail through fault and cleft and bubble, with disaster following their steps. Finally the ruin and destruction came to an end as they reached the last steep slope downward to the great sealed cleft. "What happened?" asked Robin, as they paused at last to catch their breath. "The explosions!" gasped Peter. "The concussions of our pistols shattered the delicate balance of the honeycomb undersurface here. We're lucky it didn't all come down at once, rather than in the form of a chain reaction. We're lucky to be alive, believe me!" "Yes," said Robin, beginning to make his way down the last tunnel that led to the open ledge of the great bubble-world where the Glassies lived. "Yes, we're lucky to be alive, but how will we ever get back to the surface now? We're sealed in. Maybe forever." Peter was silent as they reached the ledge, looked into the vastness of the cleft-world, saw the faint flickering lights of Moonworm and Moonman. "Maybe we'll never get out. Robinson Crusoe lived twenty-eight years on his island before he was rescued. It may be fifty before they find us in here." Robin shrugged. "When I first landed here, I said to myself that while there's life there's hope. Now there are two of us. And that's an advance...." _19. Riding the Tornado_