Croquemitoufle (1959)

Returning from a two-year stay in Terre Adélie, explorer Bernard Villiers meets up with his best friend, Thomas Desjardins, whose diplomatic duties call him to London. While Thomas is away, Bernard learns that Catherine, his wife, has run off with his collaborator Michel. Out of friendship for Thomas, and always resourceful, he follows the couple and tries to separate them. He does so much, in fact, that he falls in love with Catherine.