Trivia: Sidney Lumet's first choice for Hercule Poirot was Alec Guiness, with Paul Scofield as his second choice. Because they both were busy with other projects, Albert Finney was chosen, even though Lumet felt he was too young for the role.
Trivia: The dream sequence in which Harry tries to talk to Ann was originally meant to take place in real life (within the film, that is). The production didn't have time to finish the scene and the fog effects looked too phony. But rather than scrap the scene entirely, editor Walter Murch came up with the idea to include the footage as a dream.
Trivia: The voice of Mr. U.N. Owen on the tape is that of Orson Welles.