France, 1855. Zélie Fontaine, a twenty-odd-year-old widow and the post mistress of the small provincial town of Argenson, has accepted to receive love letters to Hortense de la Jacquerie, the prefect's wife, under her name. But Hortense decides to break up with her lover, François du Portal. François will not hear of it and, with a view to regaining her love, manages to be appointed deputy prosecutor in Argenson. Trouble can't help following.