Professor Sylvain Mithouard seems like a paragon of virtue to his family's eyes.A man with a sense of duty, he has created a stifling atmosphere in his household.However ,he leads a double life : claiming he's living for the Clermont-Ferrand congress, he actually goes to meet his young mistress.While he is away,his daughter , Huguette, tells her mother she is pregnant by her boyfriend ,a simpleton named Hervé. The whole family is terrified :how will the worthy father react when he comes back?