Thin ragged spires reared overhead, stabbing at the stars. Furtive glints of light came and went in ebon depths. The cave opened before them, and their torches showed glistening walls dropping sheer away into blackness. Falken uncoiled a thousand-foot length of synthetic fiber rope from his belt. It was no larger than a spider web, and strong enough to hold Falken and Avery together. He tied it to each of their metal boots to and let it down. It floated endlessly out, the lead weight dropping slowly in the light gravity. Eight hundred, nine hundred feet. When there were five feet of rope left in Falken's hand it stopped. "Well," he said. "There _is_ a bottom." Paul Avery caught his arm. "You aren't going down?" "Why not?" Falken scowled at him, puzzled. "Stay here, if you prefer. Sheila?" "I'm coming with you." "All right," whispered Avery. "I'll come." His amber eyes were momentarily those of a lion caught in a pit. Afraid, and dangerous. Dangerous? Falken shook his head irritably. He drove his alpenstock into a crack and made the rope fast. "Hang onto it," he said. "We'll float like balloons, but be careful. I'll go first. If there's anything wrong down there, chuck off your other boot and climb up fast." They went down, floating endlessly on the weighted rope. Little glints of light fled through the night-dark walls. It grew hot. Then Falken struck a jog in the cleft wall and felt himself sliding down a forty-five-degree offset. Abruptly, there was light. Falken yelled, in sharp, wild warning. The thing was almost on him. A colossus with burning eyes set on foot-long stalks, with fanged jaws agape and muscles straining. Falken grabbed for his blaster. The quick motion overbalanced him. Sheila slid down on him and they fell slowly together, staring helplessly at destruction, charging at them through a rainbow swirl of light. The creature rushed by, in utter silence. Paul Avery landed, his blaster ready. Falken and Sheila scrambled up, cold with the sweat of terror. "What was it?" gasped Sheila. Falken said shakily, "God knows!" He turned to look at their surroundings. And swept the others back into the shadow of the cleft. Riders hunted the colossus. Riders of a shape so mad that even in madness no human could have conceived them. Riders on steeds like the arrowing tails of comets, hallooing on behind a pack of nightmare hounds.... Cold sweat drenched him. "How can they live without air?" he whispered. "And why didn't they see us?" There was no answer. But they were safe, for the moment. The light, a shifting web of prismatic colors, showed nothing moving. They stood on a floor of the glassy black rock. Above and on both sides walls curved away into the wild light--sunlight, apparently, splintered by the shell of the planet. Ahead there was a ebon plain, curving to match the curve of the vault.