Summary. It was Cousin R, and for no want of money nor fear of exposure, but because a man arranged by his own habits had at last been brought to the one arrangement that could never again be disturbed; here is how I came to it.

The Reckoning. The puncture at the back of the neck, the dry decanter proved sound, the absence of disorder — all of it said the same thing before I had troubled myself over motive at all. Nothing in that study had been done except the one thing. The Colonel sat where he always sat, in the attitude he always took, and the only alteration in the room was a fortnight old: his wife's portrait, carried down and turned to face the chair while he was away at Inveraray. A killer who disturbs nothing, who signs nothing, who adds nothing to a room but a body already dressed in its daily posture, is not hiding his work. He has already finished it. The murder was the last brushstroke on a canvas begun two years before.

The household gave me money first, as households will. Effie Strange stood to inherit, and owed more than she could own to; but the will lay unsigned, the Colonel had said at table he'd settle nothing before Christmas, and she was in the morning-room with Xerxes and Aziz the whole of the window, each vouching the others. Lady Lavinia had two hundred a year dangled before her and unrefused; but she never left the table until the company rose, and died with the offer, not by it. Zane had his wages raised that very evening before the soup — no dismissal in prospect, and Mrs Gow had him in her sight at the foot of the back stair the whole time but for the five minutes of the decanter, at both ends of which the Colonel was alive and talking. Fifi never crossed the hall at all, kept to the dining-room and pantry under her brother's eye and the housekeeper's. Dr Quill's case lay dry in the hall, every needle in its slot, and he was at the piano with Nan and Lady Lavinia in plain sight of one another from half eight. None of them wanted the Colonel dead badly enough to answer for the twenty minutes that mattered, and none of them had those twenty minutes to answer for.

Cousin R had both. He left the table at 8:40, by his own word to take the air, and nobody saw him again until 9:05. The hall door stood opposite the morning-room, but its occupants had their backs to it, turned to their own talk; the service door was under Mrs Gow's eye and nobody passed it. That left the hall door unwatched, and Cousin R unaccounted for, for exactly as long as the thing required. He had carried the poison folded in a chemist's paper and dropped the sliver on the carpet without troubling to retrieve it — a small carelessness, but then he had never meant the room to look disturbed, only finished. A fine needle beneath the collar-line, a swift poison, and a man who does not even trouble to shift in his chair: that is not a killing got up in haste. That is a killing already rehearsed, two years of notebook entries deep — where the chairs stand, what hour the port is taken, which door is used — brought at last to its only possible conclusion.

I had nearly set the file down without the notebook, which holds no names, only placings, and seemed at first no more than an eccentric's habit. But a man who records a household's arrangements for two years, and in a fortnight's absence moves a dead woman's portrait to face a living man's chair, has told you plainly what he thinks a composition wants. The Colonel's grief, locked behind a séance door for eleven years and never once named at his own table, was the one thing in that house left unfinished. Cousin R did not kill him for gain, nor out of any grievance the dining-room could name. He killed him because a rigid man seated dead among the grief he would never own was a work worth completing, and because to leave it half done any longer had become, to a man of that temperament, nearly unbearable. It gained him nothing else, and he did not want anything else. I have charged him accordingly. The third this twelvemonth, by my count, and I confess I had hoped, this time, for an ordinary one.

Cousin R kept order as the morning settled down,
The Colonel faced his portrait in a most becoming gown.
A needle did its business, swift and small,
And conversation carried through the hall.
The moral, dear householders, is to leave things as they're found,
Though we shall move the chairs when no one is around.