Married to a businessman who abandons her, Laurence cheats on him with Mauliaire, a young actor. Letters and photos of the young woman addressed to her lover are stolen by a blackmailer who claims a large sum in return. Distraught, Laurence goes to find Master Tom Savier and deploys such a persuasive charm that the lawyer complies with her demands and decides to get her out of this mess. But he is quickly spotted by the blackmailer. In the meantime, Laurence disappears. Following a visit to Mauliaire, Tom discovers that the woman he has met is not Laurance, but Lydie Audry, the industrialist's mistress. As for Laurence, her mutilated corpse is discovered at a level crossing. Crime? Accident ? Suicide? Commissioner Muller is in charge of the investigation and casts his suspicions on the blackmailer. After many adventures, the real culprit will be unmasked.