Summary. It was Aziz, and not for gain but for love of a kind the household never named; here is how I came to it.

The Reckoning. The fall itself tells the tale before anyone else does. Quill left the gallery at 9:10 saying he would look in again, hat and gloves already on — a man leaving, by his own account. Yet he went up, not down; and the only thing at the top of that stair worth going up for was the cedar closet, standing two inches ajar with its key in the outside lock. His glove carried cedar dust, and so did the closet's inner handle. He had not gone to fetch his coat. He had gone to look again at what he had seen on Tuesday, and to be sure of it before he carried it to a clergyman that evening. The rucked runner was Mrs Gow's own work undone by somebody else's hand after eight o'clock, meant to read as a trip; it is not the work of a man who trips, but of a man who wants it to look as though one had. Eight seconds at the stair-head, no cry, no scuffle — Fifi heard the thud and nothing before it, which is what you get from a single push and no argument.

The circle at the round table clears itself entire. The Colonel, Nan, Lavinia and Effie sat hands joined from nine until the noise broke them, and not one of them stirred from that table in the material minutes; I need no more than that, though each had reason enough besides. The Colonel bullied Quill in company and paid him late, which is the temper of a man untroubled by his doctor, not afraid of him. Nan lost, in Quill's death, the one friendship the house afforded her, and it was she who noticed his Tuesday turn and spoke of it freely, having nothing to hide. Lavinia's preparation was compounded by Quill's own hand in the spring and never mentioned by him in eight months since; nothing there was newly at risk. Effie's account was renewed without difficulty on the Tuesday, with a further bottle promised her within the week — a doctor keeping a patient, not threatening to cut one off. None of the four had cause against him this particular week, which is the only week that signifies.

That leaves the one person the household forgot to ask about, because he does not sit at séance tables and was thought to be nowhere but at Xerxes's elbow. He was seen going up with a tea-tray at 8:55; after that, nothing accounts for him until the fall. The closet is not the Colonel's, and its key lives in Xerxes Hartfield's room, not on Mrs Gow's board — a fact nobody troubled to remark on, the household having long since stopped asking what Xerxes keeps upstairs and why. Quill had seen inside it on Tuesday, gone white, taken no port, and spent the week after failing to get an answer from its owner by letter — two notes marked private, both ignored — until, frightened past patience, he asked that afternoon to have the Reverend Gaunt brought to the house. A physician is bribable, in the way of most men; a clergyman, in Quill's estimation, was not. That request is what moved someone from anxiety to arithmetic.

I will own I nearly overlooked one small item, though it wants no cleverness to read, only the noticing. Aziz wears at his throat a stone no companion's wages could purchase, worn always, sold never, questioned by nobody in the house — and the closet holds its match, and the letters that go with it. What Xerxes is to him, and he to Xerxes, is an attachment of long standing that neither man had any wish to see aired before a minister of the Kirk, and it is no part of my office to name it; it is entirely my office to say that it is what killed Quill. The doctor was no danger to Aziz. He was a danger to Aziz's whole arrangement of the world, purely by being frightened and honest and about to talk, and Aziz did not sit down to reason out the size of the threat. He went out to the landing behind him and removed it, in eight seconds, without heat, and went back to his master's tea things as though the evening had not changed at all.

I make it the third such business this twelvemonth at the Manor, and I confess I am tired of the address. Aziz will be charged with the wilful killing of Dr Tobias Quill. What passed between him and Xerxes Hartfield before that Friday is their own history, and closed with this file; what it drove one of them to is mine, and is closed also.

They'll whisper a fortnight the hand it was cold,
that Aziz was in it, the whole of it told.
And Quill, the colder, is carried the door,
and Cairnholm's acquaintance the fewer by four.
We'll vow to be watchful, we'll counsel more care —
and mean not a syllable, ever, we swear.