Mrs. Hubbard: Don't you agree the man must have entered my compartment to gain access to Mr. Ratchett?
Princess Dragomiroff: I can think of no other reason, madame.
When Poirot and Mr. Ratchett first meet in the restaurant car, Poirot has to correct Ratchett's pronunciation of his name. Poirot then points with his right hand toward Ratchett, but when it cuts to a close-up of Poirot, both his hands are on the table. The angle changes back, and Poirot's hand is once again lifted.
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.