Summary. It was Aziz, and he did it to keep a secret that was his own life, not his money nor his name — here is how I came to it.

The Reckoning. Lavinia died by hand, between 10:20 and 10:55, in the ante-room off the gallery, the house's second stair unwatched for the whole of that window save by nobody. Dr Quill set the time; the bruising showed fingers and nothing else; nothing in the room was taken, posed, or tidied, which told me at once that whoever did this did not come to arrange a message, only to stop one. The sitting-book gave the message plainly enough: a locked room at Hartfield House, and a second man kept in it. There is such a room. Xerxes carries its key on his own person and lets no servant near it. Aziz is the second man, and has been for six years, on a footing the house does not discuss and I will not either; it is enough to say that his roof, his place, and the ring he wears were none of them his own earning, but Xerxes's gift, and a man so placed has nothing behind him if the gift is ever taken back. Lavinia had sat twice at Hartfield House at Xerxes's own asking, had been refused the upper floor, and had begun — first aloud, then in ink — to ask why. That is not a servant's secret or a lover's indiscretion to the ordinary eye; to Aziz it was the whole of his standing in the world, and he removed it entirely, and at once, which is the mark of a man guarding something he cannot afford to see even dented.

The rest of the house falls away easily enough. The Colonel was in the library with Xerxes from 10:25 to the alarm, each vouching for the other, and the fee quarrel had been settled that very morning, so there was nothing left between him and Lavinia to kill her over. Nan was in the gallery with Cousin R in full view of her until 10:50, clearing candles, and he of her; neither had the other out of sight for the death to be done. Fifi was belowstairs under Mrs Gow's eye until 10:55, and went up only after the window had closed, with the tray that found the body. Zane stood at the carriage-yard door from 10:30, under the coachman's and the stable-boy's watching, for the whole of the time in question. Cousin R, besides being accounted for by Nan, is in any case the wrong shape of killer for an unarranged room; he is a man who tidies everything he touches, and this room was left exactly as the act had left it, which is not his habit.

Aziz told the company he was going to the smoking-room by the west stair, and so he did — but he did not stay there. The west stair gave onto the gallery as readily as it gave onto the smoking-room, and the gallery's far end, where Nan and Cousin R worked by candlelight, was no great distance for a man moving quietly past it in the dark the sitting had left behind. He went in, did the thing with his own two hands, quickly, and came out the way he'd gone, down to a smoking-room where the fire was never lit and the cigarettes were never touched, and sat out the rest of the evening in the cold until the alarm called him up again with the rest. I had near forgotten the small matter of his fez, which Zane swears was not on the hall table at nine and was there by the time the household gathered — a man does not carry his hat down to smoke a cigarette and back up again for nothing, unless the going down was not all he did. It is not evidence a court much needs, with the rest standing as it does, but it closed the thing for me all the same.

He had no quarrel with her, no debt to her, nothing of hers he wanted. He had only a life that could not survive being read, and a woman who had begun, gently and without malice, to read it. That is motive enough, and more than enough, for what his hands then did. I have charged him. The year's third, by my count, and not yet Michaelmas.

Aziz returned from smoking air with nothing much to say,
And Lavinia found the ante-room a quiet sort of stay.
No ribbon had been rearranged, no silver plate was moved,
The fez joined all the other hats, as if the thing improved.
The moral, gravely stated, is that strong hands should be stayed,
A point the Club will note at once, and promptly let evade.