The girl Joey (Brie Larson) was abducted by a man named "Old Nick" and imprisoned by him in a shed in the backyard of his house for seven years. During this period, she was raped and gave birth to her son Jack (Jacob Tremblay). Relying on Old Nick's occasional supplies, the mother and son lived a difficult life. Despite this, the mother did her best to create a safe and happy growth space for her son Jack. This small and cramped room has become a magical little world for Jack to live and grow. After Jack spent his fifth birthday, his mother decided to tell him the truth that there is a wider world outside this small room. They began to plan an escape plan, determined to escape from the room where they were imprisoned... This film is adapted from Emma Donahue's novel of the same name.