At times the shelf would be twenty or thirty feet in width or even more, and then the going was easy enough; but at other times the space would contract to something like a yard, and then it was quite another story. Indeed, once or twice Milton Rhodes himself, an experienced and fearless mountain-climber, was glad, I believe, that the way was no narrower. As for what those moments meant to me--well, I never posed as a mountaineer or a steeple-jack. For fifteen minutes or so, I believe, we toiled along that terrible place, and then of a sudden came the end. Nothing before us but the bare precipitous rocky wall and the black profundity of the chasm, and up above a ghostly thing crawling, crawling down, ever down, and filling the place with thunder--the fall itself. Where did the water come from? From one of the glaciers? And, a question more interesting, where did it go? "We must go back," said Milton Rhodes. "The road to Drome does not lie here." Scarcely had we turned when I started, and then I cried out sharply. "Look!" I said, pointing with my alpenstock down the cavern. "Look at that!" Far down the cave a light was gleaming, where a moment before no light had been. And on the instant another shone beside it. A second or two, however, and they had vanished. "Moving," was Rhodes' explanation. "The bearers of those lights moved behind something." "No!" I told him. "They didn't move. They just went out. And look! _Again!_" There the lights were again--gleaming at us for all the world like the dim and baleful eyes of some waiting monster. Chapter 18 "THAT'S WHERE THEY ARE WAITING FOR US!" For some moments those yellow eyes gleamed at us, then vanished. The lids of that waiting monster (so to speak) had closed over them. I had watched them very intently, and I was sure that there had been no movement of the eyes themselves. Milton, however, was just as sure that they had moved. "To the right or to the left?" I queried. "Neither. Down," said Rhodes. "Then it must have been straight down." "It was. Down behind a rock-mass or something." We waited, watching closely, but those yellow eyes did not gleam again through that Stygian gloom. "Must have been at quite a distance," I remarked at last. "It seems so, Bill; and that means that this cavern is very straight for a mile or more or that it is one of enormous size." "It may be both." "It may be, of course," he nodded. "And it may be that those lights were not so far away as they appeared to us to be. One may easily be deceived in such matters." "We don't know what this means," I said; "but we know this: we're spotted." "Oh, we're seen, all right, Bill. Our every movement will be watched." Some minutes passed, during which we stood peering down the cavern and waiting; but no light gleamed forth again. Then we started back.