I think I felt it snap before I saw it. My own machine gave a sickening lurch and a long black crack appeared across the shelf—and widened. Then the ledge began to upend. I heard a scream as McIvers’ Bug rose up and up and then crashed down into the crevasse in a thundering slide of rock and shattered metal. I just stared for a full minute, I think. I couldn’t move until I heard Jack Stone groan and the Major shouting, “Claney! I couldn’t see—what _happened_?” “It snapped on him, that’s what happened,” I roared. I gunned my motor, edged forward toward the fresh broken edge of the shelf. The crevasse gaped; I couldn’t see any sign of the machine. Dust was still billowing up blindingly from below. We stood staring down, the three of us. I caught a glimpse of Jack Stone’s face through his helmet. It wasn’t pretty. “Well,” said the Major heavily, “that’s that.” “I guess so.” I felt the way Stone looked. “Wait,” said Stone. “I heard something.” He had. It was a cry in the earphones—faint, but unmistakable. “Mac!” The Major called. “Mac, can you hear me?” “Yeah, yeah. I can hear you.” The voice was very weak. “Are you all right?” “I don’t know. Broken leg, I think. It’s—hot.” There was a long pause. Then: “I think my cooler’s gone out.” The Major shot me a glance, then turned to Stone. “Get a cable from the second sledge fast. He’ll fry alive if we don’t get him out of there. Peter, I need you to lower me. Use the tractor winch.” I lowered him; he stayed down only a few moments. When I hauled him up, his face was drawn. “Still alive,” he panted. “He won’t be very long, though.” He hesitated for just an instant. “We’ve got to make a try.” “I don’t like this ledge,” I said. “It’s moved twice since I got out. Why not back off and lower him a cable?” “No good. The Bug is smashed and he’s inside it. We’ll need torches and I’ll need one of you to help.” He looked at me and then gave Stone a long look. “Peter, you’d better come.” “Wait,” said Stone. His face was very white. “Let me go down with you.” “Peter is lighter.” “I’m not so heavy. Let me go down.” “Okay, if that’s the way you want it.” The Major tossed him a torch. “Peter, check these hitches and lower us slowly. If you see any kind of trouble, _anything_, cast yourself free and back off this thing, do you understand? This whole ledge may go.” I nodded. “Good luck.” They went over the ledge. I let the cable down bit by bit until it hit two hundred feet and slacked off. “How does it look?” I shouted. “Bad,” said the Major. “We’ll have to work fast. This whole side of the crevasse is ready to crumble. Down a little more.” Minutes passed without a sound. I tried to relax, but I couldn’t. Then I felt the ground shift, and the tractor lurched to the side.