Summary. It was Dr Tobias Quill, and for no wrong done him, only a wrong he could not stop imagining; here is how I came to it.

The Reckoning. Cousin R died of a fall down twenty-two stone steps at an unlit, unrailed gallery arch, and the household's first thought was an accident long threatened by the Colonel's unmended stair. It was not an accident. There is no mark on the body but the fall itself, no draught, no glass, no sign that a physician's black bag was ever unbuckled that evening — Mrs Gow will swear it stood in the hall untouched from the moment Dr Quill arrived to the moment he was called to certify the death. Whoever put Cousin R down that stair used nothing but two hands and the dark. The watch and the ring and the eleven shillings were left on him, and the memorandum book too, lying open in his breast pocket for anyone to read. A man killed to silence a blackmailer takes the book. This one did not, because there was nothing in it to silence — only small notes on people who had never known they were watched, and among them two lines about a physician twice at a study door, and a housekeeper's honest answer that the physician had never once been mentioned. That is a thin gruel to hang a man for, and yet it was the whole of the case, because the case existed only in Dr Quill's head, built there stone by stone out of his own old debt to a certificate he signed for Mr Peachey three years since, a debt he has never stopped expecting to be called in.

The rest of the room clears itself without much labour. Nan stood in the one lit patch of the drawing-room, turning pages at Effie's shoulder from a quarter to nine until twenty past, seen there by twenty-odd people whenever they lifted their eyes from the keys; she never went near the gallery door. Effie herself never dropped a bar in that stretch, by the Colonel's own testimony, and cannot have been at the keyboard and at the head of a dark stair in the same twenty minutes. Xerxes sat at the Colonel's elbow the whole evening and the Colonel sat at his, each the other's alibi without either meaning to furnish one, and both were still in their chairs when the lamp was called for. None of them had anything to fear from a notebook that named no one and asked nothing of anybody — Cousin R collected; he never spent. The household read that as harmlessness. Dr Quill read it as a case being built, and the more the man said nothing to him, the surer he became that the silence was the shape of a file waiting to be closed on him.

So at nine he excused himself over the port, went out by the gallery door, and found Cousin R standing at the head of the unlit stair — put there by nothing more sinister than habit, a man who liked to watch a room from its edges and had wandered out to do the same to an empty gallery. Quill took him by surprise at the open arch, where there is no rail to catch a man nor a lamp to show him the danger, and shoved him down with both hands. Twenty-two steps did the rest; the hat came off some way above where the body settled, which is how a fall generally arranges these things, and no one else's arrangement was required. Fifi passed the top of that same stair ten minutes before with her tray and swore the gallery was empty behind her; the doctor had not yet gone out. The single noise the company heard and mistook for a slamming door was Cousin R's neck breaking on the flags. Quill came back through the drawing-room, sat down, and was in his seat, composed, when Zane went to look and found nothing to see in the dark. Being coroner as well as physician, he then had the singular convenience of writing his own verdict, and wrote it: a fall, instant, no mark but the fall. It is the third such reckoning I have been called to write for this house this twelvemonth, by my count, and I do not doubt I shall be sent back before the year is out. Dr Tobias Quill will answer for the killing of a man who had never made a case against him, and never meant to.

They'll whisper a fortnight the hand it was cold,
that Quill was in it, the whole of it told.
And Cousin R, 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.