"Yes; I heard it that time, too," said Milton Rhodes. "Where did it come from?" I shook my head. "Maybe one of the sounds that the glacier makes," he proffered. "It is possible. But--" "Well?" "It seemed to come right out of the rocks; but that isn't possible." "We'll see about that, Bill." He pressed a button, and the strong rays of his electric light played upon the dark rock and the blue ice. The light in his left hand, he dropped to his knees and looked under. I heard an exclamation and saw him move forward. At that instant a sound brought me up and whirled me around. My heart was in my throat. I could have sworn that the sound had issued from some point just behind me. But there was nothing to be seen there--only the walls of blue ice and the blue sky above. "Must have been some sound made by the glacier slipping or something," I told myself. I turned--to find that Milton Rhodes had vanished! For a little space I stood staring and wondering, then called in a low voice: "Milton. Oh, Milton." No answer. "Milton." Silence still. "Milton," I called once more. "Where are you?" The answer was a scream, a scream that threatened to arrest the coursing blood in my veins--the sound seeming to issue from the very heart of the rock-mass there before me. Chapter 15 THE ANGEL The scream ceased as suddenly as it had come. I drew my revolver, snapped on the electric light, and, stooping low, looked into that spot where, a few moments before, Milton Rhodes had so suddenly and mysteriously disappeared. Nothing but the unbroken rock before me. And yet Rhodes had vanished. I turned the light full upon the low roof, and then I exclaimed aloud: the entrance was there! I dropped to my hands and knees and moved under, the pack not a little impeding my movements. An instant, and I was standing upright peering into a high, narrow tunnel, which some convulsion of nature, in some lost age of the earth, had rent right through the living rock. Nothing was to be seen, save the broken walls, floor and roof, deep, eerie shadows crawling and gliding as the light moved. The view, however, was a very restricted one, for the gallery, which sloped gently upward, gave a sudden turn at a distance of only thirty feet or so. What awaited me somewhere beyond that turn? For a few moments I listened intently. Not the faintest sound--nothing but the loud beating of my heart. What had happened to Rhodes? "Milton!" I called softly. "Oh, Milton!" No answer came.