Returning from the Middle East aboard the famed Orient Express, the Belgian detective Hercule Poirot expects a quiet three-day journey across Europe. The train is unusually full for the season, carrying a cross-section of strangers: an English governess, a stiff army colonel, a voluble American widow, an aging Russian princess, a wealthy man's young secretary, and a businessman named Ratchett who confides to Poirot that his life has been threatened and tries to hire him as a bodyguard. Poirot refuses. In the night the train runs into a snowdrift in the wilds of Yugoslavia and stops dead, cut off from the world. By morning Ratchett lies dead in his locked compartment, stabbed a dozen times, and the killer can only be one of the passengers still trapped aboard. At the request of his friend M. Bouc, a director of the railway line, Poirot agrees to investigate. With no police, no escape, and the snow holding everyone in place, he questions each traveller and weighs a tangle of contradictory clues, false alibis, and a scrap of evidence pointing to an old American tragedy. As the accounts refuse to align, Poirot must reason his way toward a solution that tests his own sense of justice.