A year after the end of the First World War, Anna mourns the loss of her fiancé Frantz, who has been killed in action. One day, a Frenchman shows up at the grave and makes an appearance at Anna's in-laws, with whom she lives. Adrien introduces himself as a friend of Frantz, from his Paris student days. He is taken in by them and tells them about earlier times. But Adrien has a secret...