The Mysterious Affair at Styles recap

Invalided home from the war, Captain Hastings goes to stay at Styles Court, where his friend John Cavendish lives on the money of his elderly stepmother, Emily Inglethorp, who has just married a much younger man the whole family distrusts. Mrs Inglethorp dies in the night of strychnine poisoning behind a bolted door, hours after a violent quarrel and after making and apparently destroying a new will. Hastings brings in Hercule Poirot, a Belgian detective living among refugees in the village. Suspicion falls on the husband, but Poirot works to protect him, then dismantles the case against him in public. Instead the family closes in: John Cavendish is arrested and tried. Poirot finds the letter everyone has been looking for hidden in a vase, and shows that Alfred Inglethorp and Evelyn Howard, secretly cousins and lovers, poisoned Mrs Inglethorp between them, using her own sleeping powders to delay the dose and inviting suspicion that could be safely destroyed later. John is acquitted, and the guilty pair are arrested.

Captain Hastings, on sick leave from the Front, accepts an invitation from his friend John Cavendish to convalesce at Styles Court in Essex. The house belongs to John's stepmother, Emily Inglethorp, a wealthy and managing old lady on whose allowance the family lives. She has recently married Alfred Inglethorp, a bearded man twenty years her junior whom the entire household believes to be after her money. Also at Styles are John's reserved wife Mary, his diffident brother Lawrence, Cynthia Murdoch, a young dependant who works in a hospital dispensary, and Evelyn Howard, Mrs Inglethorp's blunt and devoted companion. Miss Howard says openly that Mr Inglethorp is a fortune hunter, quarrels with her employer over it, and leaves the house. In the village Hastings meets an old acquaintance, Hercule Poirot, a retired Belgian detective living among refugees whose lodging Mrs Inglethorp pays for. Tension in the house grows; on the afternoon of the 17th of July Mrs Inglethorp is heard quarrelling violently with someone in her boudoir, drives into town, and returns tired and secretive, taking her papers to bed with her.

In the small hours the household is woken by Mrs Inglethorp in convulsions behind her locked bedroom door. The doors to the adjoining rooms are bolted as well and have to be forced. She dies before the doctors can do anything, and Dr Bauerstein, a London toxicologist staying in the village, says at once that the symptoms are those of strychnine. Her husband is not in the house. Hastings walks to the village and asks Poirot to take the case; Poirot agrees on condition that he is allowed to pursue it to the end in his own way. Examining the sealed bedroom he notes a coffee cup ground to powder in the grate's fender, a small stain on the carpet, an overturned table, a scrap of dark green fabric caught on the bolt of the door into Cynthia's room, and, in the fireplace, a charred fragment of a will made that very afternoon. The despatch case in which Mrs Inglethorp kept her private papers has been forced open and something taken from it. Poirot learns that she had summoned her solicitor and made a new will only hours before she died.

Analysis confirms strychnine, and the question becomes how it was administered, since the coffee and the cocoa she drank both test clear and the poison acted far later in the night than it should have. At the inquest the evidence turns against Alfred Inglethorp: a chemist's assistant testifies that he sold strychnine to a man he took to be Mr Inglethorp, who signed the poison book in that name; the destroyed will was believed to have been in his favour; and he flatly refuses to say where he spent the evening of the murder. Miss Howard is recalled and repeats her opinion with force. The coroner's jury returns wilful murder against a person or persons unknown, but the village and the police are in no doubt. Hastings expects Poirot to hand the man over. Instead Poirot announces that his object is to prevent Alfred Inglethorp's arrest, and will not explain why.

When the police are ready to make the arrest, Poirot forces the issue in front of Inspector Japp of Scotland Yard: he demonstrates that Inglethorp can account for the crucial evening with witnesses who cannot be shaken, and that the chemist's evidence therefore proves only that somebody impersonated him. A false black beard is found in the attic dressing-up chest, recently used. Attention swings back to the household. Poirot pursues small things that nobody else considers evidence: the shred of green fabric, an extra coffee cup that has vanished, the papers taken from the despatch case, Lawrence Cavendish's white face in the sickroom, and Mary Cavendish's movements in the night. Dr Bauerstein's habit of tramping the countryside after dark, and his friendship with Mary, attract suspicion of their own. Relations between John and Mary Cavendish deteriorate to open estrangement.

Dr Bauerstein is arrested, but for espionage rather than murder; his night walks had nothing to do with the poisoning. Then the police act on the evidence they have assembled and arrest John Cavendish, whose quarrel with his stepmother, chronic need of money and unexplained purchase of a false beard tell heavily against him. He is committed for trial. Mary, shaken out of her reserve, admits to Hastings that she was in her mother-in-law's room that night and that the torn green fabric was hers; she had gone in hoping to find a document of her own concern. Poirot, who could have destroyed the prosecution's case at once, holds back, telling Hastings only that a single missing link would make everything certain. The trial goes badly. Counsel for the defence can shake nothing, and the verdict looks a foregone conclusion.

Poirot finds the missing link: the letter taken from the despatch case, rolled up and hidden in a spill vase on the boudoir mantelpiece, where nobody had thought to look. It is a note from Alfred Inglethorp to Evelyn Howard, and it proves that the two are secretly cousins and lovers who planned the murder together. Miss Howard's public loathing of him was a blind. She bought the strychnine in the village disguised in a false beard and glasses, signing his name so that the evidence against him would be certain to collapse; Alfred deliberately refused to explain his movements, intending to be tried, acquitted, and so put beyond a second prosecution. The strychnine was added to Mrs Inglethorp's bromide sleeping powders, so that her tonic delivered a concentrated dose days later, at an hour when both of them could show they were elsewhere. Poirot's obstruction of the early arrest is what makes the true case possible. The pair are taken. John Cavendish is acquitted and reconciled with Mary; Lawrence, who had suppressed evidence in the belief that Cynthia was implicated, becomes engaged to her; and Hastings, refused by Cynthia, leaves Styles with his faith in Poirot complete.

Poirot recovers the missing letter, which had been rolled up and pushed into an ornamental spill vase on the mantelpiece of the boudoir. It proves that Alfred Inglethorp and Evelyn Howard are secretly cousins and lovers who planned the murder together. Miss Howard's loudly advertised hatred of him was cover; it was she, disguised with a false beard and glasses, who bought strychnine at the village chemist's and signed his name, so that the evidence pointing at him could be demolished at will. The poison was worked into Mrs Inglethorp's bromide sleeping powders, so that her medicine delivered a concentrated fatal dose days later, with both of them apparently elsewhere. Alfred courted suspicion deliberately, planning to produce an unshakeable alibi at his trial and be acquitted beyond any second prosecution. Poirot's refusal to let him be arrested too early is what makes the case against him possible. The pair are taken into custody. John Cavendish is acquitted and reconciles with Mary, whose coldness had been jealousy rather than indifference. Lawrence Cavendish and Cynthia Murdoch become engaged, Hastings having proposed to Cynthia himself and been gently refused. Dr Bauerstein's night walks are explained by his arrest as an enemy agent, unconnected with the murder. Hastings leaves Styles with his admiration for Poirot confirmed, and the two agree to work together again.