Ratchett is Cassetti.

The identity of the murdered man is the central revelation that unlocks the entire mystery of the Orient Express crime. The passenger who called himself Samuel Edward Ratchett is unmasked as Cassetti, the criminal who orchestrated the kidnapping and murder of three-year-old Daisy Armstrong. This discovery, made by Hercule Poirot through a charred fragment of a letter, transforms the investigation from a conventional murder inquiry into something far more complex: a collective act of vengeance carried out by a self-appointed jury of twelve people, each of whom had been personally devastated by the Armstrong tragedy.

The Armstrong Case and Cassetti's Guilt

The Armstrong kidnapping case was a notorious American tragedy. Colonel Armstrong, an Englishman who had won the Victoria Cross, married Sonia Armstrong, the daughter of the celebrated actress Linda Arden. Their only child, three-year-old Daisy Armstrong, was kidnapped, and an impossibly high ransom was demanded. After the parents paid two hundred thousand dollars, the child's dead body was discovered; she had been dead for at least a fortnight. The shock caused Mrs. Armstrong, who was expecting another baby, to give birth prematurely to a stillborn child, and she herself died. Her broken-hearted husband shot himself. Cassetti was arrested as the head of the gang, but through the enormous wealth he had piled up and the secret hold he had over various persons, he was acquitted on a technicality. He would have been lynched by the populace had he not been clever enough to escape, changing his name to Ratchett and leaving America to live as a gentleman of leisure, travelling abroad and living on his rentes.

The Revelation of Identity

Poirot discovers Cassetti's true identity through a tiny scrap of charred paper found in the dead man's compartment. Using a spirit stove and curling-tongs, he reconstructs the fragment, which reads "—member little Daisy Armstrong." This single clue tells Poirot the dead man's real name and why he had to leave America. When Poirot reveals this to Hector MacQueen, the secretary is astonished and declares, "The damned skunk!" MacQueen explains that his father was the district attorney who handled the case, and that he had seen Mrs. Armstrong more than once—"she was a lovely woman. So gentle and heartbroken." He adds, "If ever a man deserved what he got, Ratchett—or Cassetti—is the man. I'm rejoiced at his end." The revelation spreads through the train, and Mrs. Hubbard, upon learning the truth, exclaims, "Well! Well, to think of that! I must write and tell my daughter."

The Conspiracy of Twelve

Poirot's final solution reveals that the murder was not the work of a single assassin but of a self-appointed jury of twelve people, all connected to the Armstrong tragedy. The passengers included: Linda Arden herself, disguised as Mrs. Hubbard; Countess Andrenyi, who was Helena Goldenberg, the younger sister of Mrs. Armstrong; Mary Debenham, who had been the governess in the Armstrong household; Greta Ohlsson, the nurse who had cared for little Daisy; Antonio Foscarelli, the family chauffeur; Edward Masterman, Colonel Armstrong's former batman and valet; Pierre Michel, the Wagon Lit conductor, who was the father of Susanne, the French nursemaid who had committed suicide after being wrongly suspected; Cyrus Hardman, who had been in love with Susanne; Colonel Arbuthnot, Colonel Armstrong's best friend; Hector MacQueen, whose father had prosecuted the case; Princess Dragomiroff, who was Sonia Armstrong's godmother; and Hildegarde Schmidt, who had been the family cook. Each person in turn entered Ratchett's darkened compartment and stabbed him, so that no one knew which blow actually killed him. The twelve wounds corresponded to the twelve members of the jury.

Thematic Significance

The Ratchett-Cassetti identity reveals the novel's central moral and legal dilemma: what happens when the justice system fails to punish a clearly guilty man? Cassetti escaped American law through wealth and technicalities, but the twelve people he destroyed—directly or indirectly—found their own form of justice. Poirot's final solution presents two alternatives to the authorities: the official story of an outside assassin who escaped, or the truth of a collective execution. The company director M. Bouc chooses the first, saying, "In my opinion, the first theory you put forward was the correct one—decidedly so." The novel thus leaves the reader to decide whether private vengeance can ever be justified when the law fails, and whether the twelve executioners are murderers or instruments of a higher justice.