The famous private detective Hercules Poirot returns to the United Kingdom aboard the Oriente Express from Istanbul. At that time of year, in the middle of winter, the train is usually almost empty, but this time it is unusually full and Poirot only gets a berth thanks to his friend Monsieur Bouc, director of the Compagnie Internationale des Wagons-Lits. When a certain Mr. Harris does not appear, Poirot takes his place, along with a young American named Héctor MacQueen. The second night, Poirot gets a compartment for himself, which he hands over to M. Bouc. Room 411 of the Pera Palace Hotel in Istanbul, where Agatha Christie is believed to have written Murder on the Oriente Express. During the trip, one of the passengers, Mr. Ratchett, an American millionaire, tells Poirot that his life is in danger. He shows him a small pistol that he carries he will always get to protect himself. He wants to hire Poirot to find out who is threatening him, but Poirot refuses because he "doesn't like the face" of Ratchett.