Summary. It was the maid Fifi, lent up to Hartfield House for the week, and she killed him to stop a letter — here is how I came to it.

The Reckoning. Gaunt died in the side passage between nine o'clock and half past, of one blow to the back of the head, struck by someone shorter than himself and standing behind him — Dr Quill was plain on that point, and a tall man does not stoop for a servant's step in the dark. The lamp had been trimmed full at eight and was found turned down to a bead, the wick still warm, which told me the hand that dimmed it and the hand that swung the mallet were the same hand and the same minute. One of the two gardeners' mallets stood missing from its fellow and was found flung against the wainscot; the passage floor, tracked to a uniform brown with potting soil by every soul in the house that evening, gave me no print worth the name, and the hat beneath him, claimed by nobody, told me only that somebody had wished the finding of him to look other than it was. I set the hat aside. It had done its work and I had no further use for it.

The house's first instinct was to look upward — at what Gaunt might have known of his betters. Zane had no live quarrel with him, Gaunt being ignorant of his attachment to Lady Lavinia, and stood at the dining-room sideboard the whole of the death window under four pairs of eyes. Aziz had the same alibi and no motive besides, Gaunt having said nothing of Xerxes's household to anybody. Cousin R was on the terrace among the tubs with a gardener who never left his side, and had said at table he hoped to know Gaunt better — no man arranges to lose a curiosity he has only just acquired. Effie was at the piano before six witnesses, and whatever Gaunt had written of her was old news, settled months since. Captain Wat was held in the pantry over a bill and had nothing to gain from a dead cleric; his trade wants live customers, not corpses. Each of these I set down and closed, one by one, for want of opportunity or want of cause, and each closing left the true matter plainer.

It was smaller than any of them, and closer to the ground. Gaunt had spent that week not prying into the great house's private arrangements but asking after the conduct of servants in the town, and he had told his own churchwarden he meant to write to a mistress before Sunday about a maid he had seen there — a letter that ends a place and follows a woman to the next one, and the one after that, in a town the size of Cairnholm. Fifi had been seen twice that week in circumstances she would not have wished repeated, and once by a man in a black hat who stopped to look at her a second time in the street. She was fetching linen the length of that passage all evening, with nobody to vouch for her and nobody to contradict her, and she is a small woman, and the blow that killed Gaunt came from below, struck by someone his own height's inferior. She turned the lamp down on an errand she had reason to make unwitnessed, took up the mallet standing where it had stood all day, and waited for a man who walked that passage every week and would not have turned for her.

I had very nearly closed the file without the hat, thinking it a poor blind and no more — but a woman with no place of her own that week, borrowed in from another household, had reason above any other soul in that house to leave behind a thing that was not hers, so that the finding might point elsewhere before it pointed at her. It was a small deceit, and it very nearly answered.

She has confessed it, plainly and without much crying about it, which I set down in her favour though it changes nothing in the charge. It was her place she killed for, and I cannot call that a small thing, whatever the law will call it. The third this twelvemonth, by my count, out of that same unhappy house, and I have written the charge and sent it up, and expect, before the year is out, to be sent for again.

Fifi took the garden mallet and waited in the dark
And Gaunt came from the library, remarking on a spark
He found the passage altered by a thump behind the head
The hat remained upon the floor, the moralist was dead
The moral, let us all be kind, and never make a fuss
This excellent resolve was not observed by any of us