The story begins on the Orient Express, where a wealthy businessman, Ratchett, is found murdered in his compartment. The train is stopped in Yugoslavia due to a snowdrift, and detective Hercule Poirot, who is also a passenger on the train, is asked to investigate the crime. As Poirot begins to question the passengers and gather evidence, he uncovers a complex web of relationships and motives that lead him to the surprising truth.