Cassetti kidnapped and killed Daisy Armstrong.

Cassetti, the mastermind behind the kidnapping and murder of three-year-old Daisy Armstrong, was the man who, under the alias Samuel Edward Ratchett, met his death on the Orient Express. His crime against the Armstrong family set in motion a tragedy that claimed multiple lives and, years later, brought together a self-appointed jury of twelve people who carried out a collective execution in a snowbound train carriage. The kidnapping and its aftermath form the emotional and moral core of the mystery, transforming a detective story into a meditation on justice, vengeance, and the limits of the law.

The Crime and Its Immediate Victims

Cassetti was the head of a gang that kidnapped three-year-old Daisy Armstrong, the only child of Colonel John Armstrong and his wife Sonia Armstrong. The kidnappers demanded an impossibly high ransom, and the parents paid the enormous sum of two hundred thousand dollars. Despite the payment, the child's dead body was discovered; she had been dead for at least a fortnight. The shock of the discovery caused Mrs. Armstrong, who was expecting another baby, to give birth prematurely to a stillborn child, and she herself died. Her broken-hearted husband, Colonel Armstrong, shot himself. The family was destroyed: the father, the mother, and the child all dead within a short span.

The Indirect Victim: Susanne

The tragedy did not end with the Armstrongs. A French or Swiss nursemaid named Susanne, who had been devoted to Daisy, came under police suspicion. The police were convinced she had some knowledge of the crime and refused to believe her hysterical denials. In a fit of despair, the poor girl threw herself from a window and was killed. It was proved afterwards that she had been absolutely innocent of any complicity in the crime. Susanne was the only child of Pierre Michel, the Wagon Lit conductor on the Orient Express, a fact that would later explain his willingness to participate in the conspiracy against Cassetti.

Cassetti's Escape and the Conspiracy

Cassetti was arrested but, by means of the enormous wealth he had piled up and the secret hold he had over various persons, he was acquitted on some technical inaccuracy. He would have been lynched by the populace had he not been clever enough to give them the slip. He changed his name to Samuel Edward Ratchett and left America, living as a gentleman of leisure, travelling abroad. The Armstrong family's friends and servants, driven by grief and a sense of justice denied, decided that the sentence of death that Cassetti had escaped had to be carried out. Twelve people, including Colonel Arbuthnot (Colonel Armstrong's best friend), Hector MacQueen (whose father had been the district attorney on the case), and Linda Arden (Mrs. Armstrong's mother, the actress), formed a jury and planned the execution. They tracked Cassetti down, placed two of their number in his employment, and arranged for him to travel on the Orient Express on a night when Pierre Michel, Susanne's father, would be on duty.

The Execution and Its Justification

On the night of the murder, each of the twelve conspirators entered Cassetti's darkened compartment and stabbed him. The nature of the wounds—twelve in total, some feeble, some powerful, some left-handed, some right-handed—reflected the diverse hands that struck. The conspirators saw themselves as carrying out a sentence that society had failed to deliver. As Linda Arden, disguised as Mrs. Hubbard, explained, it was not only that Cassetti was responsible for her daughter's death and her child's, but that there had been other children kidnapped before Daisy, and there might be others in the future. Society had condemned him; they were only carrying out the sentence. The crime was presented to the detective Hercule Poirot as an impossible puzzle, but he ultimately deduced the truth: that the murder was a collective act of private vengeance, a jury of twelve people executing a man who had escaped the law.