Summary. It was Dr Quill, and for fear, not for gain; here is how I came to it.

The Reckoning. Nan Pringle died of another man's sleeping draught, poured into her own cordial before ever the company sat down, and the man who poured it was the one who sat with her afterward and wrote her death up in his own coroner's hand. Two glasses of her blackcurrant cordial stood on the sideboard among the port things before the guests had so much as arrived. One was drunk, one was not. Dr Quill took his port at that sideboard, as he always did, unremarked because it was habit — and it was in that unremarked moment that Xerxes's chloral, missing from his coat some days before and dispensed originally by Quill's own hand, went into the glass meant for Nan. She drank it at the séance table. He pronounced her dead, and the household, weary of séances and sudden ends alike — the Manor's third this twelvemonth, by my count — thought it had lost a poor relation to some old grievance over the Colonel's will.

The household's first thought ran to money — Nan and Effie Strange named together in the Colonel's expectations, and a poor relation is always a convenient corpse when there's an inheritance in the air. But Effie was on the road to town and back that whole afternoon, her hour fixed by her own coachman and by Mrs Gow, and never near the Manor while the glasses stood waiting. The Colonel sat at the head of his table from the moment his guests began arriving, vouched by the same housekeeper and the company entire; he never went near the sideboard in the interval that mattered. Xerxes, whose draught it was, spent that interval closeted with the Colonel in the study, and came to the table only when the séance was called — no unwatched minute in which to dose a glass he never approached. His companion Aziz took his tea in the small parlour, under the housekeeper's eye, and joined the table late. Lady Lavinia was dressing her instruments in full view of the arriving guests. Cousin R sat across from Nan from before the cordial was even poured. Below stairs, Zane kept the door and never entered the drawing-room but to announce a guest; his sister Fifi was about the corridors, out of the room entirely; Captain Wat Frew was kept waiting in the hall unadmitted. Each of them wanted either the means, the moment, or both.

Quill wanted for neither. He is accounted the ablest hand with a draught in the district, and it was his draught, whatever coat it had lately rested in. He had the moment — his port at the sideboard, so ordinary a thing that no one thought to watch him at it. What he lacked, until lately, was reason. Nan Pringle had known him since they were children together in the same village; she was, by every account, the one soul in that household he had never had cause to fear. That had changed. Her letter to the Colonel, broken off mid-sentence, sets down plainly that she had grown certain of a physician's habit and could no longer keep it to herself, "even for an old friend." She meant Quill, and she meant to finish that sentence. A frightened man does not wait to be finished. He is the one man who had walked with her in the garden that very afternoon, easy as old friends are easy, and it was that ease — not any scheme over money, not any secret of Xerxes's he needed to bury — that told me why she alone, of the whole company, had to be silenced before she could write another word. He did not fear the house. He feared the one person in it who had stopped being safe.

I have charged Dr Tobias Quill with the wilful poisoning of Nan Pringle. The vial is his, the glass is accounted for, and the letter, unfinished as it is, says enough. The file may close.

Old Quill poured port with a trembling hand,
And Nan took cordial, as was planned,
The sleeping draught in blackcurrant sweet,
Made her collapse into her seat,
The coroner spoke with practiced ease,
And closed the case to no one's unease.