As I looked, the whole circumstances seemed to come to me. "See," I cried to Marjory, "this was evidently another entrance to the cave. The tides, ebbing or flowing, drove in through one way and out at the other; and the floor was worn level in process of countless years by rolling pebbles like these. Then came some upheaval or wearing away by water drift of supporting walls of rock; and this mouth of the cave fell in. We must be by now somewhere at the Cruden side of Whinnyfold; we are facing almost due north." As there was manifestly nothing to be done here, we took our way back to the main cavern. When we began to look around us for a new place to explore, Marjory said: "There doesn't seem to be any treasure cave at all here. We have now tried everywhere." Then it was that my mind went back again to the Don's description "Black on the one hand and red on the other." "Come," I said, "let us go back till we find the joining of the gneiss and granite." As we went back the floor was almost dry; only a few pools of water here and there, lying in the depressions, called attention to the fact that we were under tidal influence. As we went we kept a careful look-out for the fusion of the rocks; and found it where the passage with the descending roof debouched into that which led from the blocked up entrance of the cave. There was here, however, no sign of another passage, and the main one outside was like that under my own house, entirely through the gneiss. I could not help feeling a little disappointed. For many weeks my mind had been set on finding the Pope's treasure; and though I believe it was not greed which controlled me even to any great extent, I was deeply chagrined. I had a sort of unworthy fear that it might lower me in the eyes of Marjory. This feeling, however, was only momentary; and when it went, it went for good. Drawing in my note-book a rough outline of Whinnyfold, I dotted lines where I took the various branches of the cave to lie and then marked in the line of fusion of the gneiss and the granite as it was manifest on the cliffs and on the shore beyond. Marjory was at once convinced; indeed when I saw my surmise put down in black and white it seemed to me quite apparent that it must be correct. The treasure cave must be within that space which lay between the dismantled entrance on the side of the Skares, and that which had fallen in on the north side. The logical inference was that if there was an entrance to be found at all it would be close to the debris from the Don's explosion. So we took in silence, our way back to that point and began at once to examine the debris for any sign of an opening in the rock to the north side. Marjory scrambled up to the top of the pile whilst I explored the base. Turning my lantern on the rocky wall I began to examine it foot by foot and inch by inch.