1945: World War II is over, but Grace Stuart is still waiting for her husband to return home. In her remote mansion, Grace raises her two children, Anne and Nicholas, according to strict religious principles. The shutters and curtains of the house are always closed, because the children suffer from a strange illness: they are allergic to light. After one day the entire staff has disappeared without a word, Grace hires three new servants. When they disregard the most important rule of the lady of the house, sinister incidents occur.