Murder on the Orient Express is a detective novel by Agatha Christie featuring the Belgian detective Hercule Poirot. It was first published in the United Kingdom by the Collins Crime Club on 1 January 1934. In the United States, it was published on 28 February 1934, under the title of Murder in the Calais Coach, by Dodd, Mead and Company. The U.K. edition retailed at seven shillings and sixpence and the U.S. edition at $2.00.
The U.S. title of Murder in the Calais Coach was used to avoid confusion with the 1932 Graham Greene novel Stamboul Train which had been published in the United States as Orient Express
Upon arriving at the Tokatlian Hotel in Istanbul, private detective Hercule Poirot receives a telegram prompting him to cancel his arrangements and return to London. He instructs the concierge to book a first-class compartment on the Orient Express leaving that night. However this becomes impossible when it is revealed that in an unusual occurrence for the time of year (December), the train is fully booked and Poirot only gets a second-class berth after the intervention of his friend M. Bouc who is a director of the train line Compagnie Internationale des Wagons-Lits and is also boarding the train. After boarding, Poirot is approached by Mr Samuel Ratchett, a malevolent, elderly American he initially saw at the Tokatlian. Ratchett believes his life is being threatened and attempts to hire Poirot but, due to his distaste, Poirot refuses. "I do not like your face, Mr. Ratchett," he says.
On the second night of the journey, as he is only travelling to Italy M. Bouc gives up his first class-compartment to Poirot who is going to Calais and on to London (Bouc sleeps in the Pullman Coach which has only one other occupant, a Greek doctor named Constantine). This gives Poirot the compartment next to Mr. Ratchett. The train is stopped by a snowdrift near Vinkovci. Several events disturb Poirot's sleep, including a cry emanating from Ratchett's compartment. The next morning, M. Bouc informs him that Ratchett has been murdered and asks Poirot to investigate, in order to avoid complications and bureaucracy when the Yugoslav police arrive. Poirot accepts.
After Poirot and Dr. Constantine examine the body and Ratchett's compartment, Poirot ascertains Ratchett's real identity, and possible motives for his murder. A few years before, in the United States, three-year-old heiress Daisy Armstrong was kidnapped by a man named Cassetti. Cassetti eventually killed the child, despite collecting the ransom from the wealthy Armstrong family. The shock devastated the family, leading to a number of deaths and suicides. Cassetti was caught, but fled the country after he was acquitted. It's suspected that Cassetti used his considerable resources to rig the trial. Poirot concludes that Ratchett was, in fact, Cassetti.