"I took up the two other enlargements, both of the chancel, as you will remember, and commenced to compare them. For some minutes I examined them without being able to distinguish any difference in the scene they portrayed, and then abruptly, I saw something in which they varied. In the second enlargement--the one made from the flashlight negative--the dagger was not in its sheath. Yet, I had felt sure it was there but a few minutes before I took the photograph. "After this discovery I began to compare the two enlargements in a very different manner from my previous scrutiny. I borrowed a pair of calipers from the photographer and with these I carried out a most methodical and exact comparison of the details shown in the two photographs. "Suddenly I came upon something that set me all tingling with excitement. I threw the calipers down, paid the photographer, and walked out through the shop into the street. The three enlargements I took with me, making them into a roll as I went. At the corner of the street I had the luck to get a cab and was soon back at the castle. "I hurried up to my room and put the photographs away; then I went down to see whether I could find Sir Alfred Jarnock; but Mr. George Jarnock, who met me, told me that his father was too unwell to rise and would prefer that no one entered the Chapel unless he were about. "Young Jarnock made a half apologetic excuse for his father; remarking that Sir Alfred Jarnock was perhaps inclined to be a little over careful; but that, considering what had happened, we must agree that the need for his carefulness had been justified. He added, also, that even before the horrible attack on the butler his father had been just as particular, always keeping the key and never allowing the door to be unlocked except when the place was in use for Divine Service, and for an hour each forenoon when the cleaners were in. "To all this I nodded understandingly; but when, presently, the young man left me I took my duplicate key and made for the door of the Chapel. I went in and locked it behind me, after which I carried out some intensely interesting and rather weird experiments. These proved successful to such an extent that I came out of the place in a perfect fever of excitement. I inquired for Mr. George Jarnock and was told that he was in the morning room. "'Come along,' I said, when I had found him. 'Please give me a lift. I've something exceedingly strange to show you.' "He was palpably very much puzzled, but came quickly. As we strode along he asked me a score of questions, to all of which I just shook my head, asking him to wait a little.