Summary. It was the Reverend Gaunt, and the woman he killed was never the woman he meant to kill. He came into that dark house to silence the one man who had seen him at his private penance and could unfrock him with a word; he took a hat and a height and a pair of shoulders for that man, and put his cord round the wrong twin's neck. Here is how I came to it.

The Reckoning. The cord tells the tale before anything else does. Household twine does not come knotted seven times to a ring, and no shop in Cairnholm sells a discipline of that make. A man does not carry such a thing on his person unless he wears it against his own skin, and a man does not wear such a thing unless the wearing is a secret he would kill to keep. So the murderer owned the cord, and the cord was the whole of his motive: not proof of a crime already done, but the instrument of a crime committed to prevent one being known.

The house had gone black at 9:20, every jet drowned together, and stayed so until Mrs Gow brought candles at 9:40. In that twenty minutes the drawing-room party accounts for itself entire — the Colonel in his chair, Nan and Lavinia hand in hand either side of him, none letting go, none able to slip out unmissed. The business-room does the same for Wat, Xerxes, and Aziz, three men shut up together and each vouching the other two; and Aziz besides had no thread running to this household at all, Fifi's one closely kept secret being her brother's, not the Hartfields'. The billiard-room gives Cousin R and Effie to each other by candlelight the whole while, and it was Cousin R's own books, left a fortnight in the study, that had put Fifi on that errand — a man does not contrive to have his own volumes fetched down in order to murder the girl fetching them. Quill was belowstairs with Zane's rash from 9:05, Mrs Gow passing the open door twice to prove it; he could no more have been in the library than the maid could have been in two places.

That leaves the Reverend, waiting alone at the stair-head from the moment the gas failed, and unaccounted for the whole twenty minutes. He had come, he said, only to walk his sister home. He had also, some weeks before, been surprised at a private devotion by a footman who thought nothing of it and told no one but his sister — and told her only as an oddity, not a confidence. Zane did not know he held a secret worth a man's ruin. But Gaunt could not know that. A minister who holds himself to a hard, secret penance, and who is seen at it, lives from that hour with the fear of the telling, whether or not the telling was ever meant.

In the dark he heard a servant moving above and followed. He found a figure of Zane's own height, back turned, arms full of books, a man's black felt hat set square on the head — and took it, in that blindness, for the footman he had come to silence. He looped the cord and drew it and never saw the face. He left the cord because a warm garrote in his own pocket was a worse hazard than an unremarkable strap left behind in the dark, and because he could not risk being found searching for it. Then he went back down and stood in the hall as though he had never moved.

What undid him was Mrs Gow's candle at 9:50, and Zane coming up the back stair alive. She saw the Reverend's face at that moment, and a man does not go white to the lips and clutch a chair-back at the sight of a footman with a rash unless he had believed, until that instant, the footman already dead.

His contempt for Fifi was real and loud and long-standing, and the house has been glad enough to suppose he throttled her for her sins, her hats, her men on the back stair. That reading costs him nothing and explains nothing, for it was never her he came for. What he was guarding is his own affair, and I shall not set the word for it in this file; what it drove him to is mine, and it drove him to garotte a woman who had never done him harm, in mistake for a man who had never meant him harm either. Self-preservation, and nothing more dignified than that — the third such letting of blood this twelvemonth, by my count, and I am told to expect no fourth, though the house has not yet given me reason to believe it. He is charged, and the file is closed.

Gaunt in the darkness made fatal mistake,
And Fifi in books found her final brake,
The gas-lamps had failed in that airless room,
A figure in shadow met gasping doom,
The cord was his terror, his knot and his fall,
We learn to see faces before we enthral.