Stephen Norton

Stephen Norton (aka Mr. X) is the main antagonist of Agatha Christie's novel Curtain: Poriot's Last Case and one of the foremost antagonists of the whole novels about Hercule Poirot. He disguised himself as an innocent man, but he is responsible for numerous murders Poriot investigates.

Aidan McArdle portrays Norton in the TV episode adaption of Curtain, which is also the whole TV series' final episode. Therefore, Norton is the final villain of Poirot series, in both books and TV series.

Plot of Curtain
A person is unsuspected of involvement in five previous murders, in all of which there was a clear suspect. Four of these suspects have since died (one of them hanged); in the case of Freda Clay, who gave her aunt an overdose of morphine, there was too little evidence to prosecute. Poirot calls the recently widowed Hastings to join him in solving this case. Poirot, using a wheelchair due to arthritis, and attended by his new valet Curtiss, will not share the name, using X instead. X is among the guests at Styles Court with them. The old house is a guest hotel under new owners, Colonel and Mrs Luttrell. The guests know each other, with this gathering initiated when Sir William Boyd-Carrington invites the Franklins to join him for a summer holiday stay. The five prior murders took place in the area, among people known to this group.

Elizabeth Cole tells Hastings that she is a 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 is stigmatised by the trauma. Three incidents occur in the next few days, showing the imprint of X. First, Hastings and others overhear an argument between the Luttrells. Shortly afterwards, Mr Lutrell wounds his wife with a rook rifle, saying he mistook her for a rabbit. Mrs Luttrell recovers, and the incident has a good effect on their marriage. Next, Hastings is concerned that his daughter Judith spends time with Major Allerton, a married man. While Hastings and Elizabeth are out with birdwatcher Stephen Norton, Norton sees something that disturbs him through his binoculars. Hastings assumes it has to do with Allerton. When his attempts to persuade Judith to give Allerton up merely antagonise her, the worried father plans Allerton's murder. He falls asleep while waiting to poison Allerton, relieved he took no action when he awakes the next day. Last, Barbara Franklin, wife of Judith's employer Dr Franklin, dies the following evening. She was poisoned with physostigmine sulphate, an extract from the Calabar bean that her husband researches. Poirot's testimony at the inquest, that Mrs Franklin had been upset and that he saw her emerge from Dr Franklin's laboratory with a small bottle, persuades the jury to return a verdict of suicide.

Norton is still concerned over what he saw days earlier when out with Hastings and Cole. Hastings advises Norton to confide in Poirot. They meet in Poirot's room. That night, Hastings is awakened by a noise and sees Norton entering his bedroom. The next morning, Norton is found dead in his locked room with a bullet-hole in the centre of his forehead, the key in his dressing-gown pocket and a pistol nearby.

When Hastings tells Poirot that he saw Norton return to his room the night before, Poirot says it is flimsy evidence, not having seen the face: the dressing-gown, the hair, the limp, can all be imitated. Yet, there is no man in the house who could impersonate Norton, who was not tall. Poirot dies of a heart attack within hours. He leaves Hastings three clues: a copy of Othello, a copy of John Ferguson (a 1915 play by St. John Greer Ervine), and a note to speak to his long time valet, George. After Poirot is buried at Styles, Hastings learns that Judith has all along been in love with Dr Franklin. She will marry him, and leave to do research in Africa. When Hastings speaks to George, he learns that Poirot wore a wig, and that Poirot's reasons for employing Curtiss were vague.

Four months after Poirot's death, Hastings receives a manuscript in which Poirot explains all. X was Norton, a man who had perfected the technique of which Iago in Othello (and a character in Ervine's play) is master: applying just such psychological pressure as is needed to provoke someone to commit murder, without his victim realising what is happening. Norton had demonstrated this ability, with Colonel Luttrell, with Hastings, and Mrs Franklin. Poirot intervened with sleeping pills in Hastings' hot chocolate that night, to avert a disastrous rash action. Ironically, Hastings had intervened in Mrs. Franklin's plan to poison her husband, by turning a revolving bookcase table while seeking a book to solve a crossword clue (Othello again), thus swapping the cups of coffee, so Mrs Franklin poisoned herself. Poirot could not prove this. He sensed that Norton, who had been deliberately vague about whom he had seen through the binoculars, would hint that he had seen Franklin and Judith, to implicate them in the murder of Mrs Franklin, not inadvertent suicide as it was. This explains Poirot's testimony at her inquest, to ensure the police would stop their investigation.

Given his very weak heart, Poirot conceives that he must end the string of murders by killing Norton. At their meeting, he told Norton what he suspected and his plan to execute him. He gave Norton hot chocolate. Norton, arrogant and self-assured, insisted on swapping cups. Poirot had drugged both cups, knowing that he had a higher tolerance for a dose that would put Norton to sleep. Poirot moved the sleeping Norton back to his room using the wheelchair. Poirot could walk, one reason he needed a new valet for this last case. Then he disguised himself as Norton by removing his wig and false moustache, ruffling up his grey hair, then donning Norton's dressing-gown and walking with a limp. Poirot was the right height. Having Hastings establish that Norton was alive after he left Poirot's room, Poirot shot Norton. He locked the room with a duplicate key. Poirot then wrote his story. He ceased taking his amyl nitrite heart medicine. He cannot say it was right to commit murder, but on balance he was sure he prevented yet more instigated by Norton. His last wish for Hastings was typical for Poirot, the matchmaker: he suggests that Hastings should pursue Elizabeth Cole.

Trivia

 * Norton is considered one of, if not the, darkest antagonists of Hercule Poirot stories alongside Franklin Clarke.
 * Like Grace Springer, Mrs. Clapperton, Henry Reedburn, Harrington Pace, Sir Reuben Astwell, Paul Renauld, Simeon Lee, Lady Boynton, Leslie Ferrier, Cassetti, Mary Gerard, Lord Edgware, Madame Giselle and Paul Déroulard, Norton is presented as a murder victim, but their depraved nature and/or former crimes soon come to light in some parts of the stories.
 * Unlike the others above, Norton's twisted nature revealed before his death, not after. What is more, the man who killed Norton is none other than Poirot himself.