Brilliant French actor Michel Simon plays Boudu, a disheveled tramp. After his dog runs away, he tries to drown himself by jumping in the river. He is saved by a middle-aged bookseller who takes the tramp into his home. Boudu shows his gratitude by taking over the bookseller's house, bedding his wife, and courting his mistress/maid.
Director Jean Renoir laughs at a middle-class businessman whose more-or-less orderly existence is disrupted by the carefree loiterer.