Summary. It was Fifi Swain, the maid, and the reason was plain enough once the household's small injuries were set in order — she had been blamed once, wrongly, over a broken decanter, and was about to be blamed again, publicly and ruinously, over the household books. Here is how I came to it.

The Reckoning. The method wants no great ingenuity, only opportunity, and opportunity belonged to one person. The devilled kidneys were Effie's own asking, named in the kitchen passage that afternoon with Mrs Gow standing by to hear it, and they were the one dish got up for her alone. Mrs Gow stood at the servery door from a quarter to eight and will swear that every plate went out named and in order, and that the kidneys passed from dish to tray under Fifi's hand and no other's. That is the whole of the method — laudanum stirred into mustard sauce, which hides a good deal, drawn from the stillroom cupboard belowstairs that every servant in the house used freely and that nobody troubled to lock. The dose Quill found was far past anything Effie herself had ever measured out, and her own bottle was found stoppered and nearly full in her reticule, which tells us the fatal draught came from elsewhere. Fifi cleared the plate to the scullery in the ordinary course of things, which is why it survived to be tested at all, and the screens did the rest — a reader behind the third could be heard and not seen, and so Effie sat silent through the whole of the second act with nobody troubling to look behind the partition until the interval.

The others fall away by the simple arithmetic of where each body stood. Zane carried trays beside his sister but handled none of the named plates himself, and stood at the drawing-room door under the Colonel's eye from before eight until the body was found; he was never near the servery bench. The Colonel read loudly and continuously from his own chair the whole evening, heard by the entire company, and had no hand in the supper arrangements at all. Nan worked the bell under the eyes of Cousin R and the Colonel and never went near the servery. Quill answered his own cues without a gap until he was called to the body, and it was he, not some more convenient party, who found and named the poison once the plate was already cleared. Lavinia was in the dining-room hunting her spectacles with Mrs Gow at the very hour the trays went in — the one place in the house that put her furthest from the kidneys. Cousin R stood at the chimneypiece in plain sight throughout. Captain Frew did not arrive until half past eight, well after the dosing, and sat with the Colonel's man in the study until the act ended. None of these had the one thing the matter required, which was five unwatched minutes with that particular dish.

The motive sits exactly where the opportunity sits — belowstairs, and nowhere upstairs at all. Effie's own troubles, the debts, the opium, the expectation under the Colonel's will, make a fine show of a reason but none of them required a maid's hand; a woman minded to end her own difficulties has her own bottle for it, and hers was untouched. Fifi's trouble was smaller and nearer: a month's wages stopped and her character threatened over a decanter she had never carried upstairs, which her own brother knew and held his tongue about; and that very afternoon Effie had sat with the household books on her knee promising the room, laughing, that she would find where the money went and that it was generally the maid. A second accusation would have turned Fifi out without a character, which for a woman in service is very near the whole of her life. The prompt copy settles what little doubt remained — the maid's cues struck through and written over in pencil, in a hand that is not Effie's and that answers, stroke for stroke, to Fifi's own. It was done in an idle moment at the servery bench, before the trays went in, and she had no time after to think better of it and take it back.

I make this the third this twelvemonth, by my count, and I am sorry to say it is the same house both other times. Fifi Swain is charged accordingly, and the file may close.

Fifi amended cues with pencil, neat and plain,
While Effie sat behind the screen in rain.
The household ate on, undisturbed and prim,
And carried the empty plate away on a whim.
The moral is patience, pronounced with a sigh;
Still, pay what you owe ere the servants reply.