Summary. It was Nan who did it — the Colonel's poor cousin, so called, who sits at the edge of every room in that house and is noticed by no one — and she did it to silence a man who meant to pull down the one roof that sheltered her. Here is how I came to it.

The Reckoning. Aziz died of Quill's own sleeping draught, tipped into his cordial and drunk alone, as was his habit, after the labelling. He never woke to know what had been done to him, which is the only mercy in the business. The draught itself told me little, for it is kept about that house like salt in a kitchen, and half the family has a bottle somewhere to hand. What told me more was the glass's company: Aziz drank the stuff alone, by arrangement, and whoever killed him had to know that beforehand. That is not common knowledge. That is a thing told to a servant that morning, by someone with reason to ask it.

I set aside Quill early, though his draught was the weapon, for the plain reason that a man does not generally poison the one person in a house who never crossed him. Quill had no quarrel with Aziz, and nothing to gain by his death; and the knowing choice of that particular cordial, at that particular hour, wanted a morning's quiet arranging that Quill, forever hurrying between dispensary and sickroom, had neither cause nor opportunity to make. I set aside the Colonel for a simpler reason still — he asked for the tray, which looks damning until one learns he took no cordial himself, and spent the whole window of the thing in the library with Xerxes over the venture papers, each vouching the other. His quarrel, such as it was, ran against the marriage and not against Aziz's person; a man does not poison his partner's companion to defend a partnership. And I set aside Zane the footman almost at once, for the kitchen had him in continuous sight all afternoon carrying sugar and jars, and the man had no stake whatever in who slept in whose rooms.

Which left the one person whose afternoon was arranged too well. Nan did not carry the tray; she saw to it that the housemaid carried it, on the Colonel's asking, and then sat herself down in the front parlour with Lavinia and Gaunt and wrote fruit labels for the whole of the relevant hour, with two witnesses to swear she never left her chair. It is a fine alibi. It is, in fact, too fine — for it was Nan who told the housemaid, that same morning, which glass was Aziz's and when he drank it, and a woman does not generally trouble herself with another man's drinking habits unless she means to make use of them.

The why of it I had from the household's own silences, which are louder in that house than its talk. Xerxes's marriage to Nan is the public face the family shows Cairnholm; what Aziz was to Xerxes privately is the household's own affair, and I will not set it down plainer than the house itself ever did. Aziz had lately taken to pressing that the truth of the arrangement be spoken aloud, out of some grievance of the heart I do not pretend to judge. But the truth spoken aloud would have ended Nan's place in that house as surely as a door shut in her face, for the marriage is the only shelter a woman in her situation has ever had. She did not strike him in anger. She arranged the morning, stepped back into a room full of witnesses, and let the cordial do the rest — the perfect absence, as tidy as the jars on the still-room table.

I had very nearly set the file down without the label — the scored-through line Aziz began and could not finish, lying among the jars like a confession he never got to make. It does not name her. It did not need to. It was enough, set beside the rest, to close the matter. Nan is charged; the marriage she killed to preserve will not survive the telling of it in any case. The third this twelvemonth, by my count, and I do not expect it to be the last out of that house.

Nan, in the parlour, maintained a calm air,
And Aziz drank his cordial alone in his chair.
The draught was well measured, the household was gay,
While Lavinia and Gaunt wrote the morning away.
The moral, we’re certain, is: trust what is poured—
We shall still let the housemaid attend to the board.