Summary. It was Aziz, the Colonel's guest without a name for what he was, and he put Nan through the gap in the balustrade because her marriage to Xerxes Hartfield would give her, in the sight of the whole parish, the very things eleven years under that roof had never given him — a ring, a place, and the ordering of the house. Here is how I came to it.

The Reckoning. The fall itself wanted no great cleverness, only darkness and ten unwatched minutes, and the house obliged him with both. The lamps had been complained of at 8:50 and nobody troubled to see to it properly — turned low at the screw, they left the gallery floor near black, which suited a man who meant to cross it unseen. At nine the curate called the pose, six figures required, and Aziz stood among them in a mantle with neither sleeve nor pocket to betray him. When the pose broke at 9:02 he stepped off the boards, went by the passage behind the gallery to the service stair — a stair no one on the platform, at the door, or in the Colonel's chair could see — and came upon Nan at the hamper, lifting drapery by a gap in the balustrade the carpenters had left unpegged. He put his hands to her. She went through, and the neck did the rest. He was back at the gallery door by 9:12, having wanted, he said, a glass of water, and one hand bare when he was seen buttoning his coat at 9:20. He is a cold-fingered man who never dines without his gloves, and its fellow was never found because he had not troubled to look for it in the dark he had made.

The rest of the house falls away easily enough, each on a plain fact rather than a character. The Colonel never left his chair, with Quill at his elbow the whole while, and neither the chair nor the doctor commands a view of a stair that cannot be seen from the gallery at all. Xerxes stood counted among the six at nine and went straight from the platform to the card-room at 9:07; he had no interval to spend on a landing. Zane stood at the door in the Colonel's sight throughout, and the door does not lead to the stair without crossing lit ground he was never seen to cross. Fifi was at her iron in the still-room, in Mrs Gow's book without a gap, and in any case the glove on the landing is a man's, too large for her hand or Lavinia's — Lavinia herself being pinned into her costume by two parish ladies from 8:55 to 9:11 and in no state to go anywhere unassisted. Cousin R stood the pose at nine and stood it again at nine-five, on the boards until the lamps went up. Wat never came further than the kitchen door, haggling over hampers with Mrs Gow beside him the entire time. Effie was set down from the Cairnholm road at a quarter past nine, five minutes after Nan was already found, and the coachman will swear to it. That leaves the household's favourite theory — that she was silenced for what the account-book knew, or for having once been let into a locked closet — a very tidy notion that wants only a murderer with something to lose by her talking, and neither Xerxes nor anyone else with a secret went near that stair. The paper in her hand said MARRIAGE, not accounts. It was jealousy, and of a particular and private kind — what the man was to Xerxes Hartfield in all but name is his own affair, and none of mine to write down; what it drove him to is mine, and I have written it. Nan had said at table that a wife has the ordering of her own house, and that was the whole of the offence she gave. I have laid the charge. It is the third this twelvemonth, by my count, and I do not expect it will be the last I am sent to that house to file.

The method was quiet, the motive was plain,
and Aziz shall never be spoken again.
Here Nan lies still, in a house full of eyes,
and none of them fancied a soul would be wise.
The whole sorry business we'll shelve with a shrug —
and sleep, and forget it, and think it no tug.