The Sleeping Car Murders

The Sleeping Car Murders French title Compartiment tueurs is a 1965 French mystery film directed by CostaGavras from the novel by Sbastien Japrisot. It stars Simone Signoret, Michel Piccoli, Yves Montand, JeanLouis Trintignant, Catherine Allgret, Jacques Perrin, Charles Denner and Pascale Roberts. This film was the first movie for CostaGavras, to be followed later by other, more politically serious work.

Source: Wikipedia