Socialite Jessica Flagmore Shelley Zsa Zsa Gabor is killed when her bed catches fire. Three years later, her adolescent daughter, Susan Susan Gordon is released from St. Marie's Convent and Hospital, after recovering from a nervous breakdown. Though deemed mentally healthy, Susan remains confused about the circumstances of her mother's death. She is now in the custody of her father, Edward Don Ameche and stepmother, Francene Martha Hyer. Susan also becomes reacquainted with her older cousin Anthony Maxwell Reed. Soon, she reads her mother's will, detailing hundreds of thousands of dollars that she will receive at age 25, and she is told she can resume living in the Flagmore mansion as long as she likes. However, its contents and furniture will be auctioned to generate income to cover losses from Edward's bad investments. Later, in private, Francene suggests Edward have Susan recommitted to gain control of her trust fund, but Edward dismisses the idea.
One evening, while haunted by disturbing visions, Susan scratches a portrait of her mother. It bleeds. She then experiences an image of Jessica bursting into flames. As a result, Susan deduces that Jessica was murdered, and evidence of this exists somewhere in the house. Later, Susan is attacked by Cousin Anthony's pet hawk. She beats it dead with one of her dolls. Inside the tattered doll, Susan discovers Jessica's valuable heirloom, a necklace. Moments later, Francene enters the room, posing as Jessica, and requests the necklace. Susan feigns mental regression. This leads to a violent altercation. The two knock over a phone receiver, through which Francene overhears Anthony on an extension phoning police to report Susan as Jessica's murderer. Later that evening, Francene confronts Anthony, and their conversation is overheard by Susan. It is revealed the two, who are lovers, conspire to steal Susan's fortune. Yet they argue how. Their plot ends when an enraged Francene murders Anthony with a large antique fishing hook.
Francene then accuses Susan of stealing her necklace, replicating the scenario that occurred between Susan and Jessica the night she burned to death. Their feud intensifies when Francene pursues Susan through the house with a pair of scissors. The chase ends in the bedroom, where Susan renders Francene unconscious before knocking over a candle and igniting the bed in flames. Edward stumbles upon the scene and puts out the fire. Francene awakens, gripping the necklace in her hand, claiming Susan killed both Jessica and Anthony. Francene then attempts to blackmail Edward with Susan's alleged culpability and threatens divorce. Edward tells Francene that it was in fact he who killed Jessica to appease Francene, who now laughs hysterically. In a rage, Edward strangles Francene just as he had Jessica. Susan appears from behind a curtain and takes Jessica's necklace from Francene's neck. She tells Edward she will help hide his crime—just as she had when he murdered Jessica—before lighting the bedroom aflame with a candle. The two exit the house, hand in hand, as it begins to burn.
