"Murder on the Orient Express" is a classic detective novel written by Agatha Christie, first published in 1934. It is one of Christie's most famous and beloved works, featuring her iconic detective character, Hercule Poirot. The story is set aboard the luxurious Orient Express train, which is traveling from Istanbul to Calais. During the journey, a wealthy American businessman named Samuel Ratchett is murdered in his compartment. The train is snowbound in Yugoslavia, providing the perfect setting for a classic locked-room mystery.

Hercule Poirot, who happens to be on board the train, is asked to investigate the murder. As he interviews the passengers and examines the evidence, he uncovers a web of lies, secrets, and motives among the eclectic group of travellers. The suspects include an assortment of colourful characters, each with their own motivations and alibis. Poirot uses his keen powers of observation, deductive reasoning, and psychological insight to piece together the clues and unravel the mystery. In a dramatic climax, he gathers all the suspects together and reveals the truth behind the murder in a classic Christie-style denouement.

"Murder on the Orient Express" is celebrated for its intricate plot, clever twists, and memorable characters. It has been adapted into numerous films, television series, radio dramas, and stage productions over the years, including a popular 1974 film adaptation directed by Sidney Lumet and featuring an ensemble cast led by Albert Finney as Poirot.