Bernard Lefrancois is a prosperous farmer on the River Marne, while his neighbor is impoverished. Lefrancois objects strongly to the romance between his son and the neighbor's daughter, but it continues in secret. WWI begins and the son becomes an aviator with the French army, and the unwed girl presents Lefrancois with an unexpected grandchild. The German army occupies the area, and the girl is serving France as a spy and securing information needed by the French to drive out the Germans. While his son is engaged in air-combat against the Germans, and the unwed mother of his grandchild is serving as a spy against their country's enemy, Lefrancois also joins the battle as a soldier.

Two middle-class notions dealers live happily with their girl, but an inheritance turns these nice people into snob Nouveaux Riches. Although the aristocracy invites them, the 'Tout-Paris' laughs behind their back. When they invite their would be new friends for a ball in their desirable new mansion, their daughter, sick and tired of being abandoned by her once loving parents, throws the invitations into the Seine.