Young Jean Rezeau lives a happy life during the 1920s with his older brother Freddy at their grandmother's home. But when their grandmother dies, they have to return to their parents, who live in another country with a third son, Marcel. Quickly, Jean and Freddy realize that their mother, Paule, is an authoritarian and incapable of tender feelings. She dominates her husband Jacques, a dreamer impassioned by the study of flies. Faced with their family's precarious financial situation, Paule imposes various deprivations and drudgeries on her children. Her cruel behavior incites Jean to carry out a rebellion.