Having concluded a case, detective Hercule Poirot (Albert Finney) settles into what he expects will be a relaxing journey home aboard the Orient Express. But when an unpopular billionaire is murdered en route, Poirot takes up the case, and everyone on board the famous train is a suspect. Using an avalanche blocking the tracks to his advantage, Poirot gradually realizes that many of the passengers have revenge as a motive, and he begins to home in on the culprit.