Rick Turner is plagued by recurring visions of a woman in a negligee dancing amid clouds, visions that disturb his peace and sense of reality. One night, compelled by his unsettling dreams, he goes for a walk and finds himself drawn to a peculiar doll shop. There, he notices a doll in the window that bears an uncanny resemblance to the woman from his visions. This discovery sets off a series of strange and increasingly disturbing events. The shop owner, Frank Lamont, who claims to know Rick's name and insists he ordered the doll, reveals that the doll is a likeness of Bianca Milan, a woman that Rick has never met.
The next day, Rick brings his girlfriend, Donna Trent, to the shop to show her the doll. Donna instantly recognizes that another doll in the shop looks just like her, but Frank refuses to sell it. As Rick and Donna prepare to leave, Frank secretly takes the Donna-like doll into a back room decorated with curtains, open-flame lamps, an altar, and a Buddha statue. In a disturbing act, he stabs the doll with a long pin, causing Donna to collapse in pain. Concerned, Rick rushes her to the hospital, where a doctor diagnoses her with a "spasm of the heart" and advises complete bed rest.
Later, Rick experiences yet another vision of Bianca. Determined to resolve this mysterious connection, he tells Donna that he plans to deliver the Bianca doll to Bianca herself, believing it might lift the strange curse. When Rick visits the doll shop again, Frank insists the doll was paid for in advance and hands it over to Rick. He then visits Bianca’s luxurious apartment, where he is captivated by her beauty. The two become lovers that very night. Bianca introduces Rick to her belief that his visions are a form of "thought projection or thought transference" — a concept she explains as a product of the cult of Gamba, the Great Devil God, of which she is a member.
Bianca persuades Rick to attend a cult meeting, which is secretly held in the back room of the doll shop. It is here that Rick discovers Frank's role as the High Executioner of the cult. During the meeting, Bianca reveals that a human sacrifice is planned: a woman is placed on an altar while a wheel studded with knives is spun above her. As the wheel lowers, Gamba, the cult’s deity, decides her fate. In a chilling display, Frank activates a mechanism that is ambiguous in control — it could be either him or Gamba pulling the lever — but the sacrifice survives as the knives are rubber.
Throughout these events, Rick notices more disturbing evidence. He finds a doll representing Donna pinned through the heart with a pin on the wall at the shop, intensifying his concern. Hoping to help Donna, Rick visits her in the hospital and promises that she will be fully cured at midnight — a prophecy that proves true when she awakens healthy and discharges herself.
In a tense turn, Donna's recovery prompts a call from Mary, a cultist and nurse, to Bianca, alerting her to Donna’s sudden healing. Later, Rick is summoned to Bianca’s apartment for an emergency cult meeting. During this gathering, Frank warns that one of them is an "intruder" destined to die at midnight. As the clock strikes twelve, Frank seizes a doll of the man who had secretly taken photographs of the cult sacrifice and jamming a pin into its head; the man, an undercover reporter, screams in agony as his car crashes down a hillside, igniting in flames as Frank burns the doll.
The meeting continues into the early hours, and Frank now tests Rick’s loyalty by bringing Donna in as a sacrificial offering. Rick, desperate to protect her, pulls her to safety as he tries to thwart Frank’s ritual. A vigorous fight ensues, culminating in Frank being struck by the spinning wheel, which kills him. The room catches fire in the chaos, and Rick and Donna manage to escape amid the flames. As they drive away together, declaring their love and believing the nightmare is over, a final haunting image appears — Bianca, once again amidst clouds, smiling and saying, "That's what he thinks!", leaving the audience with the sense that the darkness may not be fully extinguished.
