What do Cannes Cannes Express companions do when travelling back after a successful week in Cannes. There is only one option…to talk Murder Mystery and tell the tale of the Murder on the Orient Orient Express.
Hercule Poirot arrives at the Tokatlian Hotel in Istanbul. There he receives a telegram prompting him to return to London. He instructs the concierge to book a first-class compartment on the Simplon-route Orient Orient Express service, leaving that night.
Although the train is fully booked, Poirot obtains a second-class berth, but only with the intervention of a friend and fellow Belgian who is also boarding the train, Monsieur Bouc, a director of the railway, Compagnie Internationale des Wagons-Lits.
Once on board the train, elderly American, Samuel Ratchett, attempts to hire Poirot because he believes his life is threatened, but Poirot refuses out of distaste for the man.In Belgrade, on the second night of the journey, two extra coaches are added to the train and Bouc gives up his first-class compartment to Poirot and moves to a different coach himself.
That compartment adjoins Ratchett’s. The train is stopped by a snowdrift near Vincovci. Among the several events that disturb Poirot’s sleep is a cry from Ratchett’s compartment.
The next morning, Bouc informs him that Ratchett has been murdered and asks Poirot to investigate.
When Poirot and Dr Constantine examine Ratchett’s compartment, Poirot finds a trace of a burned note with the words “–member little Daisy Armstrong” on it, which leads him to doubt Ratchett’s identity. A few years before, three year-old Daisy Armstrong was kidnapped by a man named Cassetti, who collected a ransom but killed the child anyway.
Cassetti was caught but fled the country after he was acquitted on a technicality. Poirot concludes that Ratchett and Cassetti are one and the same.
Poirot proposes two possible solutions: Either a stranger boarded the train and murdered Cassetti, or every one of the passengers, all of whom were discovered to have had a connection to the Armstrong case, had all conspired to kill Cassetti together.
Mrs. Hubbard – in fact Daisy Armstrong’s grandmother – the famous actress Linda Arden, confesses the truth to be the second solution. But Monsieur Bouc and Dr. Constantine tell the Yugoslav police that it was stranger who boarded the train, murdered Cassetti, and then fled.