In times of World War I, a group of boisterous young ladies occurs to them that they could help the boys of the front writing letters to them and, thus, becoming their godmothers of war. Madeleine writes to the soldier Jacques Bertin, but, out of prudence, instead of giving her true identity, she impersonates her late grandmother. When the soldier comes on leave and wants to see her, the mistake will bring humorous consequences.