“Digby-Coates, I reasoned, _must_ have begun his preparations immediately after Belford saw him standing in the doorway of his room at eight minutes to eleven. To descend the wall; to enter the study; to hold Hoode in chaffing conversation for a moment to allay his curiosity regarding the unusual method of entry; to kill him; to reassemble the wood-rasp; to set the ‘struggle’ scene; arrange the clock; to climb back up the wall again; and all as noiseless as you please, cannot have taken him less than eight minutes at the very least. As I have shown, he was in all probability back in his room by four minutes past the hour (if not earlier) and it will be seen, therefore, that he must have begun descent of the wall by four minutes to at the latest. “The witnesses I was after, therefore, were those who thought they had seen him between four minutes to and four minutes past the hour. “Of these, as you can see from my statement of the alibi, Elsie Syme is the first, Mabel Smith the second, and Belford the third. (Elsie Syme, it is true, might be considered as barely coming within my rough-and-ready time-limit, but you must remember that all the times I fixed were calculations and not stop-watch records.) “Separately, I questioned the three servants. It was not an easy task. I had to handle them gently, and I had to impress upon them the vital necessity to forget the conversation as soon as they had left me. I think I managed it. “Their answers to my first important question were the same, though each was with me alone when I put it. “I said: ‘You say you saw Sir Arthur at such and such a time in his room on the night of the murder, and that he was sitting in his chair and that that chair was by the window. Are you certain of this?’ “They said: ‘Yes, sir,’ and said it emphatically. “I played my trump card. I played it in some fear; if the answers were not what I expected, my case fell. “I said: ‘Now tell me: _exactly how much of Sir Arthur did you see?_ What parts of him, I mean.’ “They goggled. “I tried again: ‘Was the chair that big arm-chair? And was it facing the window with its back to the door?’ “‘Yes, sir,’ they said. “I said: ‘Then all you saw of Sir Arthur was——’ “They replied, after some further help but with conviction, that all they had seen was the top of his head, part of his trousers, and the soles of his shoes. Belford, who is an intelligent man, expanded his answer by saying: ‘You see, sir, we’re all so used-like to seein’ Sir Arthur sittin’ like that and in that chair as we just naturally thinks as how we’d seen all on ’im that night.’ Which, I think, is as lucid an explanation of the mistake as could well be given.