Elected prosecutor of the Republic in a little village in the provinces, Gérard Latour lives with the family Delanglade, the young wife of the household being his mistress. A little while later, a fire ravages the factory of Mr. Delanglade. During the ensuing enquiry, the Prosecutor discovers the troubled past of industrialist and his agent Jacques Perthuis in a one-time convict. They had themselves fired the factory so as to be able to collect the insurance. Gérard latour, suspecting his mistress of being her husband's accomplice, leaves after a stormy explanation.