"Easy, baby, easy." I mumbled into her ear. "We've arrived, we're okay. Just relax." She turned her face up to mine, and I forgot to speak. Suddenly my mouth was down on hers, hard, my arms crushing her against me. We clung like that for a dizzy moment, then broke apart. "Snow," I gripped her wrists and held her there, staring at me. "Snow, darling, if we ever get out of this alive--" "I know," she breathed. "I know, Jery. I love you!" I kissed her again, gently, this time. Then we started off down the tunnel, away from Clatclit's light. I hoped he wasn't melted beyond repair. I knew, though, after that shattering exchange of affection with Snow, that I sure was! Behind us the light vanished. I looked back, but could discern neither Clatclit, nor the rock bridge, nor the torrent. "I guess we feel our way from here on in," I remarked. "No," said Snow, halting close beside me. "There, up ahead, Jery! A light." Together we moved down the tunnel. The light grew in intensity. Then we'd reached the lighted area. We were face to face with a peculiar red-bronze stone wall. No other tunnels led off from where we stood. There was no direction we could go from there except back toward that perilous underground cataract. "Could we have come the wrong way?" Snow asked. "Maybe we missed a turnoff back there in the tunnel where it was darker." "No," I said. "I had my hands feeling the walls all the way from the bridge onward, until we could see our way. This must be the right place." Then on a sudden instinctive hunch I turned to Snow. "Got a lipstick in that handbag of yours?" She looked at me blankly, but nodded, and produced the slim metal tube for my inspection. I took it from her fingers, slipped off the cap, and twirled up a half-inch of the glossy red wax. "Now let's see if I'm right about this wall," I said, and made a streaking motion across the rough surface with the lipstick. The end of the wax cylinder came away a bit disturbed by its apparent contact with the surface before us, but the wall held no trace, no mark, not even a smudge. I saw the little curls of sheared-off wax falling down the face of the wall to the floor of the tunnel. I handed the lipstick back to a bewildered Snow. "Just as I thought," I said. "That, honey, is the rock known as parabolite. The toughest, most impervious substance in the solar system. Nothing marks it, scratches it, or even budges it. We couldn't get past here with an intercontinental size collapser!" "But Jery, look!" Snow cried, pointing at the wall. I looked. The flat wall of parabolite, the impervious mineral, was going slowly concave in the center. I took hold of Snow by the shoulders, and pulled her back from that rapidly deepening hemisphere, expecting--I don't know _what_ I was expecting. But I was scared speechless.