Summary. It was Wat Frew, and for no coin at all — the one thing he could not turn to profit; here is how I came to it.

The Reckoning. Gaunt's whole living, once he took to religion, was refusal. He would not be bought, he would not be frightened, and he had said from his own pulpit that his ruin would be a mercy he had not earned. That leaves a man of Wat's trade nothing to work with. Wat deals in levers — a debt owed, a name that must not be spoken, a cargo that must not be seen — and against a man who wants none of these there is no dealing to be done. When Gaunt moved from disapproving of the smuggling to writing it down, addressed to the Collector at Leith and left unsealed in his basket like a man with nothing to hide, the last restraint on Wat went with it. A predator denied his lever has only the knife.

The method was plain enough once the linen was counted. Wat was seen going into the hot chamber at a quarter to four, and took care to be seen; that chamber has one door only, giving onto the dark stretch of corridor, and nobody troubled to watch it again once he was inside. He is not a man who takes hot baths — the crew of the Corbie Ann will tell you he washes in the sea in February and calls a warm tub an indulgence — which told me he went in that afternoon for the door, not the water. He took a second sheet from the press, which is why the count came up one short, stepped into the corridor when Dunnet was sent for water at ten past four, put out the lamp, and waited. Gaunt came through wrapped in his own sheet and Wat put a common gutting knife into his back — the sort every kitchen and every fish-hamper in Cairnholm keeps a dozen of, which is precisely why it named nobody. He dropped it where it fell, stuffed the wet sheet behind the boiler, and went back into the heat to be found there, dry and unhurried, when the shouting started.

The household first laid it at Lavinia's door, and I do not blame them; she had the coal money and decades of resentment, and it was she who asked Gaunt to the bath. But Mr Erskine had told her plainly at Whitsun that the trust falls to her only if she outlives Gaunt after the funds are released — and Gaunt had released nothing. His dying first sends every penny to the parish. She had the least to gain of anyone in the house, and she spent the whole afternoon arguing about coal in company, which is a poor way to arrange a murder that costs you money. Xerxes was in that same room, in the same company, from a quarter past three, and the brig named in the letter had passed out of his name that very morning into Wat's — the Customs letter had stopped touching him before it was ever written. Quill was fetching water with Dunnet from four o'clock and had not exchanged a word with Gaunt in eleven years; there was no quarrel there to finish. Effie's coal was laid in a week before and owed nothing to anybody. Cousin R never left the cooling room, and in any case a knife flung down beside the body is not the mark of a man who plans his removals — it is the mark of one who does not need to.

I had nearly set the file aside without troubling over the extra sheet, one more out than there were bathers, but linen does not lie, and a man who cannot swim and will not bathe hot has no honest reason to spend three-quarters of an hour behind a door that opens only onto the dark. I have charged Wat Frew with the killing of Simeon Gaunt. The third this twelvemonth, by my count, and I do not expect it to be the last out of that house.

They'll whisper a fortnight the hand it was cold,
that Wat was in it, the whole of it told.
And Gaunt, 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.