“I split the difference and took eleven-three as the time at which Digby-Coates left the study—by the window. He must have been, I argued, snugly back in his room by four minutes past at the latest. He is still an active and very powerful man, and the climb could not have taken him long.
“Having, after hearing what Belford had to tell me, thus been enabled to know at least a part of the time which must prove a weak spot in the alibi, I reviewed that itself. Before I do so, here, however, there is one more point which I must settle. It concerns the hay-fever of the aged Mr. Poole. As the attack of this malady which let Belford into the study unobserved failed to stay in his memory, it might be thought that he may have had another attack, enabling another man to enter the study without being seen. That idea, which is sure to be entertained, is, I submit, of no value. One attack is ordinary enough; but the old man tells me that he has been ‘better lately.’ Two of those painful seizures would have stayed in his mind. Besides, there is the silk rope and other evidence to prove descent by the wall. Also, the crime was obviously premeditated, and no murderer of such skill as Hoode’s would rely upon the hay-fever of an aged butler, even if he knew of its existence.
“Now for the facts of the alibi. It will be remembered that Digby-Coates had, on the night of the murder, retired to his own sitting-room at a few minutes after ten. The night was hot. He opened the window to its fullest extent; also flung the door open. This was (I use his own words, spoken at the inquest) ‘in order to get the benefit of any breeze there might be.’ Further, since he ‘wished to be alone in order to go through some important papers,’ he pinned upon that open door a notice: ‘Busy—do not disturb.’
“After he had gone to his room, the first incident with which we need concern ourselves occurred at 10:45, when Deacon made that famous request for the time. At that moment Digby-Coates was pacing the room, and Deacon, disregarding or not seeing the notice on the door, put his question from the passage.
“About seven minutes later, Belford, walking down the passage, saw Digby-Coates standing in the doorway.
“The next we hear is from Elsie Syme, one of the housemaids, who ‘saw Sir Arthur sitting in his big chair by the window’ as she passed his door. (The quotation is from her reply to a question of Superintendent Boyd’s.) So far as can be ascertained, this was not more than five minutes after Belford had passed by—making the time about 10:57.
“Next comes another housemaid, Mabel Smith, who had been working in the linen-closet, which is opposite the door of Deacon’s room. She said that returning from the journey she had made downstairs (and by forgetting which she had furnished Deacon with that false alibi which he rather foolishly tried to make use of) she had noticed Sir Arthur ‘sitting in his room.’ The time then, as guessed at by the girl and more definitely confirmed by Elsie Syme, who knew what time she had left the servant’s hall, was between eleven and one minute past.
“Next comes Belford again. You remember that he entered the study at a point between three and four minutes past eleven. On his way there from the upper part of the house he passed Digby-Coates’s room and ‘saw Sir Arthur by the window.’ Since he went straight to the study, the time at which he passed Digby-Coates’s door cannot have been earlier than 11:03.
“After this we have Elsie Syme again. This time she is on her way to bed. Passing along the passage she again ‘saw Sir Arthur sitting by the window.’ The time in this instance is a little harder to get at, but cannot have been more than six minutes past the hour.
“Last we have the evidence of old Poole, who, after entering the study on hearing Miss Hoode scream, immediately fled to fetch his dead master’s friend. He found Sir Arthur sitting with a book, his armchair pulled close up to the open window. This, since Miss Hoode entered the study at approximately ten minutes past eleven, was probably at 11:13 or thereabouts.
“That is the alibi, and a very good one it is, too—too good. It was, of course, never recognised as being an alibi, since Digby-Coates was never suspected by police or public as being the murderer; but the very fact of its being there (it trickled out mixed up with unimportant and verbose evidence, and was very cleverly referred to by Digby-Coates himself on every possible occasion) must have had its subconscious effect. (I should perhaps explain here that, as Digby-Coates was never suspected and the alibi was therefore the nebulous but effective thing I have described, the times I have given were not mentioned otherwise than generally: such exactitude as appears above is the result of Superintendent Boyd’s and my own questioning, of which more came later.)
“I have shown that according to the witnesses, none of whom I could suspect of anything but honesty, Digby-Coates was seen there in his room at times which made it impossible that he should have done the murder. Yet I knew he was the murderer. Therefore some at least of these witnesses who had sworn to seeing him were mistaken.
“I had, then, to find out (a) which witnesses were thus in error, and (b) how they had been induced to make their common mistake.
“I got at (a) like this: (if the way seem long and roundabout, remember that it is far more difficult to find things out than to understand, when told, how they were so found out):—
“Digby-Coates, I reasoned, must
