Summary. It was Effie Strange, and for the plainest reason a young woman in her situation could have: the doctor had crossed her name from his book that night, written "no further" beside it, and left the book open where a careful eye might find it. Here is how I came to it.

The Reckoning. The method was quiet, as her methods tend to be. Dr Quill kept a dispensary bottle in his bag, and Effie, who has taken laudanum daily these three years, knew the bag and its contents as well as he did. She took the bottle from it in the hall when he arrived, and kept it about her through the evening. At 9:40 he went to sit alone with his port in the library, complaining of his head; Mrs Gow set decanter and glass at 9:45 and left him to it. At ten o'clock Effie excused herself from the table for air — Gow's first opening of that door — and in the few minutes she was gone she emptied the bottle into his glass, a dose no man puts in his own drink, and was back at cards before the hand was played out. She returned nearer eleven, Gow's second opening, found him past waking, took the fellow cushion from the window-seat, and finished what the drug had begun. Then she put the room to rights: cushion returned and squared, spectacles folded, bottle dropped in the grate rather than kept about her person. It is not a killing got up to look like anything. It is a tidy woman's tidiness, applied to a body.

The house wanted to read it as Wat's business — he had been bleeding the doctor over an old certificate, and a frightened man silencing his blackmailer is a story that tells itself. But the money runs the wrong way: Quill was paying Wat, not the reverse, with a third payment promised for Lady Day that died with him, which is poor motive for the Captain to lose. And Wat cannot be fitted to the hour regardless of motive — from a quarter past ten until eleven he was in the cellar counting bottles against Mrs Gow's list, and she does not let him out of that account for a minute either side of the two openings of the library door. Zane is cleared the same plain way, seen or heard by Gow from ten o'clock through the pantry's open door, and besides has no name in the book worth protecting — physicked twice, for a chill and a cut hand, nothing against him. Cousin R was in the long gallery, seen there at twenty past ten and again at eleven, at the far end of the house from where the thing was done, and never asked the doctor for so much as a powder in his life. Lavinia sat with the Colonel and Nan from nine o'clock straight through to the alarm, on both their word together, and had come only for her Friday fee, which she'd had.

What clears the household also convicts her. Effie alone had the freedom of the card-table, up and gone twice at the hours that matter, both times inside the only windows Mrs Gow allows for that door to have opened. And she alone had reason to fear what was written on that page — not scandal of the ordinary kind, but the plain fact of a habit set down in a physician's own hand, which the Colonel need only read once to end her allowance and her expectations both. Quill had been the cheap, respectable half of her supply since she was a girl, asking no price but honesty; that night he'd resolved to withdraw it, with the ledger open on the table to prove the extent of what he was withdrawing her from. A man who is at once useless to you and dangerous to you does not often survive the discovery. I had near forgot the almonds — she'd brought them herself, and ate from the dish all evening in plain view of the table, which is not the habit of a woman planning to be doubted afterward. It seals nothing on its own, but it sits well with the rest.

Three this year, by my count, and the year not out. I have sent for her.

Effie at half-past nine had left the table,
And Quill lay dreaming in his reading-fable.
What laudanum begins, a pillow ends,
When tidy hands dispose of tidy friends.
The moral whispers: guard your written word—
Though we shall gossip till the truth is blurred.