The Coming of Mr Quin is a short story written by Agatha Christie, and was first published in 1924.
It is New Year's Eve and a house party is taking place at a country house called Royston. Mr Satterthwaite is one of the guests. His hosts are Tom Evesham and his wife, Lady Laura. Among the other guests are Sir Richard Conway and Alex Portal and his Australian wife of two years, Eleanor. Satterthwaite finds her intriguing on many counts, not least of which is the question as to why a blonde would dye her hair dark when the usual convention is the reverse. The clocks strike midnight and as the older members of the guests gather their chairs round the fire, mention is made of Derek Capel, the previous owner of Royston, who committed suicide ten years previously seemingly without reason. Tom Evesham stops such conversation and a few minutes later the women retire to bed. Satterthwaite observes Eleanor's intense looks before she leaves.
Left to their whisky and the fire, the men restart the conversation regarding Capel but they are uneasy doing so, with mentions of ghosts walking in the night. There is a sudden knock on the door and when it is opened a stranger stands there, the lights through the stained glass above the door casting a multi-coloured look over his motoring clothes. He introduces himself as Mr Harley Quin and asks for shelter while his chauffeur repairs his broken-down car. He knows this part of the world and knew Derek Capel and skilfully steers the conversation round to the events of the night in question and why Capel should suddenly take his own life. Satterthwaite cannot help but feel that Quin's appearance on this night was no accident. As the discussion continues, Satterthwaite spots the figure of a woman crouched down in the darkness at the top of the stairs listening in. It is Eleanor Portal.
Capel told the guests on the night of his death that he was about to be engaged. They all assumed that it was to a Marjorie Dilke who Capel had been seeing a lot of up to a year before when things had suddenly got a lot quieter. The way he was secret about the engagement makes Conway wonder if the engagement wasn't to someone else, such as a married woman. All agree that Capel's manner that night was like a man who had won a large gamble and was defying the odds, yet ten minutes later he shoots himself. A late post of letters and newspapers arrived, the first for several days in the snow-bound countryside but Capel didn't open any of the letters. A policeman was in the house at the time of the tragedy having found one of Capel's dogs who had strayed and been buried in a snowdrift. He was in the kitchen when the shot was fired. Quin asks them to place the exact date, possibly by reference to some event in the news and the men remember it was the time of the Appleton case murder trial. Mr Appleton was an old man who mistreated his far younger wife, and Capel was also a friend of theirs. Appleton died by strychnine poisoning but the poison was only found after the body had been exhumed. His wife had been seen to smash a decanter of port that her husband had drunk from – presumably to destroy the evidence – had been put on trial, found not guilty but left the country because of the scandal.
Quin is able to take the men through the sequence of events: Capel saw the paragraph in the newspaper that the exhumation order had been given then he saw a policeman approaching his house. He didn't know that this visit was about the missing dog and assumed that he was to be arrested and so shot himself. His audience is stunned at the accusation Capel was a murderer, objecting that he wasn't at the Appleton's on the day of the death but Quin points out that strychnine is not soluble and would collect at the bottom of the decanter even if placed there a week before. The question is asked why Mrs Appleton smashed the decanter and, at Quin's prompting, Satterthwaite theorises it was to protect Capel, not to cover her own guilty tracks.
Mr Quin leaves the house having said his goodbyes. Eleanor Portal is seen to follow him down the drive to say a thank you and then she and her husband are reconciled. Eleanor was Mrs Appleton but Capel's suicide left her unable to clear up her name totally until Quin's appearance.
The Coming of Mr Quin: First published as The Passing of Mr Quin in issue 229 of the Grand Magazine in March 1924.
In 1930 the short story, along with other Mr Quin short stories, was published in the short story collection The Mysterious Mr. Quin.
The Coming of Mr Quin was adapted into film as The Passing of Mr. Quinn in 1928.