J'ai épousé une ombre (1983)

Eight months pregnant, Hélène Georges is abandoned by her partner, Franck, in an industrial town in eastern France. Distraught, she goes to the station and boards the first train heading south. In the dining car, she meets Patricia, who is traveling with her husband, Bertrand Meyrand, the eldest son of a wealthy Bordeaux winegrower and wine merchant. He is about to introduce his young wife, who is also pregnant, to his family. After an incident in the dining car, Patricia takes Hélène to her compartment, where they chat. Patricia lets Hélène rest in her cabin. A few moments later, the train derails. After the accident, Hélène wakes up and realizes that Patricia’s in-laws have mistaken her for Patricia. Lost and with no family, she goes along with the in-laws’ assumption as they take care of her. She soon falls in love with Pierre, the brother of her supposedly deceased husband, and he falls in love with her too, with the more or less tacit approval of his parents, Matthieu and Léna Meyrand. But just as Hélène has found happiness with this family, Franck reappears and blackmails her. Franck tells Pierre’s mother about Hélène’s impersonation, and she has a stroke. During an argument, Hélène kills Franck, though she has no real intention of killing him. Pierre hides the body. As she is dying, Léna forgives Hélène, whom she loves very much, and takes responsibility for the killing so that Hélène and her son can live happily.