Janet (Elizabeth Dear & Jennie Linden), a girl at finishing school who 6 years ago saw her mother (Isla Cameron) stab her father to death, is plagued by nightmares. (Her mother, following the tragedy, was committed to an asylum.) Miss Lewis (Brenda Bruce), a teacher, takes Janet home; and in the absence of Henry Baxter (David Knight), Janet's guardian, they are met by John (George A. Cooper), the chauffeur; Mrs. Gibbs (Irene Richmond), the housekeeper; and Grace Maddox (Moira Redmond), an attractive nurse-companion hired by Henry. Miss Lewis leaves Janet in Grace's care. The nightmares continue: a white-shrouded woman (Clytie Jessop) roams the corridors, inviting Janet to burst into her parents' room where she finds the same woman on the bed with a knife in her chest. When Henry returns he finds Janet under sedation; her doctors recommend psychiatric care; but he refuses, and Janet tries to commit suicide. Henry's wife comes to tea, and because she seems to be the woman in Janet's nightmares, Janet stabs the woman to death and is promptly committed to an institution. The woman in white is revealed to be Grace, disguised with a wig and mask and in cahoots with Henry. They marry, but Grace begins believing that Henry is trying to drive her mad. Under the impression that Janet has escaped from the asylum, Grace stabs Henry to death, expecting Janet to be blamed. Janet, however, never left the asylum, and Grace is brought to justice.