I ran my eyes along the base of the rocks; I searched every spot that the eye could reach on the face or in the shadowy recesses of the dark, broken mass, towering there high above us; I looked all around at the fissured ice: but there was nothing unusual to be seen anywhere. "Where," I asked, and my tones were low and guarded, "did the angel, if the angel was here--where, Milton, could the angel and the demon have vanished so suddenly and without leaving a single trace?" "There lies our problem, Bill. A very few minutes should find us in possession of the answer--if, that is, we have not come too late. As to the vanishing without leaving a single trace behind them, that no trace was found is by no means tantamount to saying that they left none." "I know that. But where did they go?" "Let us," said Rhodes, "see if we can discover the answer." "I don't think," I observed, "that they could have gone _right into_ the rocks: either Dillingham, as he made his way here to the girl, would have seen them, or Boileau would have found the _entrance_ to the way that they took." "At any rate," Rhodes answered, "we may take that, for the moment, as a working hypothesis, and so we will turn our attention now to another quarter. If we fail there--though, remember, ice _moves_, Bill--we will then give these rocks a complete and careful examination with the object of settling the question whether the great Boileau really did see everything that is to be found here." "And so--" I began. "And so?" he queried. "Then they--or it--disappeared by way of the ice." "Precisely," Rhodes nodded: "by way of the ice. And now you see what I meant when I reminded you that the ice here moves." "Yes; I believe that I do, at last. Great Heaven, Milton, what can this thing mean?" "That is for us to seek to discover. And so we will give our attention to these crevasses." He moved to the edge of one of those big fissures that I have mentioned, the upper one, and peered down into the bluish depths of it. I followed and stood beside him. "It couldn't have been into this one," he said. "Impossible," I told him. He moved along the edge of the crevasse, in the direction of the rocks. I went along after him, my right hand near that pocket which held my revolver. "And," thought I bitterly to myself, "this is the Twentieth Century!" "They could," said Rhodes at length, stopping within a few yards of the wall of rock, "have gone into the crevasse at this point. Yes, most certainly they could have done so." "But where could they have gone to? There is no break in the wall here, not even a crack." "Don't forget, Bill, that ice moves." "If _that_ is the explanation, we shall go back no wiser than when we came."