Curtain
Agatha Christie
 The murderer, identified by Poirot simply by the letter X, has been completely unsuspected of involvement in five previous murders, in all of which there was a clear suspect. Four of these suspects have subsequently died (one of them hanged), but in the case of Freda Clay, who gave her aunt an overdose of morphine, there was considered to be too little evidence to prosecute. Hastings agrees that it is highly unlikely to be coincidence if X was connected with all five deaths, but Poirot, now using a wheelchair due to arthritis and attended by his new valet Curtiss, will not give him X's name. He merely makes it clear that X is in the house, which has been turned into a private hotel by the new owners: Colonel and Mrs Luttrell. Hastings makes certain discoveries in the next few days. Elizabeth Cole, another guest at the hotel, reveals to him that she is in fact the sister of Margaret Litchfield, who had confessed to the murder of their father in one of the five cases. Margaret had died in Broadmoor Asylum and Elizabeth feels stigmatised by the case. Later that day Hastings and several other people overhear an argument between Colonel Luttrell and his wife. Shortly afterwards, he wounds her with a rook rifle, apparently mistaking her for a rabbit. Hastings reflects that this is precisely the sort of accident with which X is associated, but Mrs Luttrell rapidly recovers. Hastings is concerned by the attentions paid to his daughter Judith by Major Allerton, whom he discovers is married but estranged from his Catholic wife. While he and Elizabeth are out with Stephen Norton, another guest and a birdwatcher, Norton sees something through his binoculars that seems to upset him. Hastings suspects that it is something to do with Allerton and, when his clumsy attempts to persuade Judith to give Allerton up merely antagonise her, he plans Allerton's murder. He falls asleep while waiting to poison Allerton, and feels differently about things when he awakes the next day. Barbara Franklin, the wife of Judith's employer Dr Franklin and the childhood friend of Sir William Boyd Carrington, dies the following evening. She has been poisoned with physostigmine sulphate, an extract from the Calabar bean that her husband has been researching. After Poirot's testimony at the inquest – that Mrs Franklin had been upset and that she had emerged from Dr Franklin's laboratory with a small bottle – a verdict of suicide is brought in, but Hastings suspects that the death was murder and Poirot confirms this. Norton, still evidently upset about what he has seen through the binoculars, asks Hastings for his advice, which is to confide in Poirot. Poirot arranges a meeting between them and says that Norton must not speak to anyone further of what he has seen. That night, Hastings is awakened by a noise and sees Norton – with his dressing-gown, untidy grey hair and characteristic limp – go into his bedroom. The next morning, however, Norton is found dead in his locked room with a bullet-hole perfectly in the centre of his forehead, the key in his dressing-gown pocket and a pistol (remembered by a housemaid as belonging to him) nearby. Apparently, X has struck again. Poirot takes Hastings over the evidence, pointing out that his belief that he saw Norton that night relies on loose evidence: the dressing-gown, the hair, the limp. Nevertheless, it seems that there is no one in the house who could have impersonated Norton, who was a short man. Hastings despairs that the mystery will ever be solved when Poirot himself dies that night, apparently of natural causes. He nevertheless leaves Hastings three conscious clues: a copy of Othello, a copy of John Ferguson (a 1915 play by St. John Greer Ervine that is now – unluckily for readers of Curtain – largely forgotten) and a note telling Hastings to speak to his permanent valet, Georges. In the weeks that follow the death of Poirot, Hastings is staggered to discover that Judith has all along been in love with Dr Franklin, and is now marrying him and going with him to do research in Africa. Was Judith the murderer? When Hastings speaks to Georges, he discovers that Poirot wore a wig, and also that Poirot's reasons for employing Curtiss were vague. Perhaps the murderer was Curtiss all along? The solution, and one of the greatest of Christie's twist endings, is contained in a written confession that is sent to Hastings from Poirot's lawyers, four months after Poirot's death. In it, Poirot reveals that he wore a false moustache as well as a wig and explains that X was Norton, a man who had perfected the technique of which Iago in Othello (like a character in Ervine's play) is master: applying just such psychological pressure as is needed to provoke someone to commit murder, where normally they would let the other live and dismiss their desires as simply the heat of the moment, without anyone ever truly realising what he is doing. Again and again Norton had demonstrated this ability, first by apparently clumsy remarks that goaded Colonel Luttrell to take a homicidal shot at his wife, and then by his careful manipulation of Hastings to resolve upon the murder of Major Allerton. It was Norton's contrivances that created the impression that Judith loved Allerton when in fact she has been in love with Franklin all along. Hastings's potential murder had, however, been averted by Poirot's presence of mind in forcing drugged hot chocolate upon him on the night that he had intended it to take place, the same action resolving Poirot to take action; he knew that Hastings was not a murderer, but if he had not intervened Hastings would have hanged for a crime while the 'true' murderer would have escaped seemingly innocent. Deprived of his prey twice, Norton turned to Mrs Franklin, who was soon persuaded to attempt the murder of her husband, after which she could be reunited with the wealthy and attractive Boyd Carrington. By an ironic twist of Fate, however, Hastings himself had intervened in this murder; by turning a revolving bookcase table while seeking out a book in order to solve a crossword clue (coincidentally Othello again) he had swapped the cups of coffee so that the one with poison in it was actually drunk by Mrs Franklin herself. Poirot knew all this but could not prove it. He sensed that Norton, who had been deliberately vague about whom he had seen through the binoculars when attempting to imply that he had seen Allerton and Judith, was now intending to reveal that he had seen Franklin and Judith, almost certainly implicating them in the apparent murder of Franklin's wife. The only solution was for Poirot to murder Norton himself. At their meeting, he revealed to Norton what he suspected and said that he intended to 'execute' him. He then gave him hot chocolate. Norton, arrogantly self-assured in the face of both the accusation and the threat, insisted on swapping cups, but both contained the same sleeping pills that had previously been used by Poirot to drug Hastings; guessing that Norton would request the swap, Poirot had drugged both cups, knowing that his time taking the pills would give him a higher tolerance for a dose that would put Norton out. With Norton unconscious, Poirot, whose incapacity had been faked (a trick for which he needed a temporary valet who did not know how healthy he was and would accept his word without question) moved the body back to Norton's room in his wheelchair. Then, he disguised himself as Norton by removing his wig, putting on Norton's dressing-gown and ruffling up his grey hair. Poirot was the only short suspect at the house. With it established that Norton was alive after he left Poirot's room, Poirot shot him – with characteristic but unnecessary symmetry – in the centre of his forehead. He locked the room with a duplicate key that Hastings knew Poirot to possess; both Hastings and the reader would have assumed that the duplicate key was to Poirot's own room, but Poirot had said that he had changed rooms before Norton's arrival, and it was to this previous room that he had the key. Poirot's last actions were to write the confession and await his death, which he accelerated by moving amyl nitrite phials out of his own reach, seeking to avoid the traditional arrogance of the murderer where he might come to believe that he had the right to kill those he deemed it necessary to eliminate. His last wish is implicitly that Hastings will marry Elizabeth Cole: a final instance of the inveterate matchmaking that has characterised his entire career.