Peggy (Judy Geeson), an unassuming twenty-two year old caregiver, has recently married Robert Heller (Ralph Bates), and is scheduled to move with him to a secluded boys' boarding school south of London for his work. The night before she is to meet Robert to leave the city, she is attacked in her home by a one-armed man with a prosthetic limb and falls unconscious. Rattled by the attack, she leaves with Robert the following morning to the boarding school, which is run by headmaster Michael Carmichael (Peter Cushing).