On a quiet vacation along California’s rugged coast, pregnant Mandy Anthony, [Peggie Castle], her husband Dick Anthony, [Arthur Franz], and her sister Kate Hazelton, [Marsha Hunt], hope for a relaxing break by the sea. But the trip takes a dark turn when Mandy suffers a seizure, loses consciousness, and miscarries, turning a hopeful getaway into a troubling ordeal. When Mandy comes to, she speaks of being Felicia and even calls Dick “Dickens.” A stunned Dick, [Arthur Franz], confesses to Kate, [Marsha Hunt], that Felicia was his first wife and that he never told Mandy about that marriage or Felicia’s death six years earlier.
Felicia, [Peggie Castle], demands to visit the Bradleys — an elderly couple who she asserts are her parents. She convinces Mrs. Bradley, [Helen Wallace], and Mr. Bradley, [James Bell], that she has truly returned from the dead. The revelation unsettles Dick, who admits to Kate that Mrs. Bradley might be dangerous and that Felicia’s return could upend everything. Meanwhile, Mr. Bradley warns, “God will punish you for this,” to which Mrs. Bradley retorts, “You believe in your god. I’ll believe in mine.”
To keep the tension rolling, Dick invites his friends John Mitchell, [Don Haggerty], and Molly Prentiss, [Evelyn Scott], to the vacation home for cocktails. Felicia attempts to harm Kate by gas in her bedroom, but Mandy’s voice unexpectedly awakens Kate in time. Outside, Felicia cruelly kills the family dog Copper, a beloved companion of Mandy.
The next day, Kate visits John’s house, where neighbor Nancy Cordell, [Marianne Stewart], drops by. Nancy casually reveals that she and the Bradleys are part of Maître Renault’s, [Otto Reichow], devil cult — a connection Felicia shares. Kate expresses curiosity, and Nancy arranges for a meeting with Renault himself.
Dick’s trust in the occult begins to unfold as Renault, distraught by Mrs. Bradley’s meddling, refuses to let Felicia be controlled by anyone else. Renault murmurs to a photo, “Now that you’ve returned, Felicia, I’ll never let you go again,” a line that goes unseen by a jealous Nancy, who stays behind and observes him.
Mr. Bradley disposes of his ties to the cult and offers to help bring Mandy back, but Mrs. Bradley menacingly warns that there are “secret ways of causing pain — pain that will end in death.” Kate grows increasingly unwell as the cult’s machinations press in, while John reveals a long-held guilt: he once found Felicia hiding in his car, and their quarrel near the cliff ended with Felicia’s death as she tumbled from the rocks after she attempted to coerce him.
A housekeeper named Agnes, though not shown in every listing, phones Dick in a panic from the Bradley residence. Dick, Felicia, and Kate rush to the house, only to discover the Bradleys dead — Mr. Bradley slain by his wife’s act, and Mrs. Bradley killed by a spell Renault casts before dying herself. The trio takes Felicia home and traps her in a locked room, but she escapes by convincing Kate she’s Mandy and then knocking Kate unconscious. Felicia then travels to Renault, arguing that Mandy must not reclaim the body they share.
Nancy warns that Renault plans to sacrifice Molly, [Evelyn Scott], to keep Felicia alive, and a determined group hurries to Renault’s residence to intervene. Dick and John wrest a knife away from Renault, but Nancy, armed with a pistol, orders them to release Renault. Renault is shot by Nancy, Felicia experiences another seizure, and the group returns Felicia home.
When Felicia awakens, she is Mandy again, and Kate resolves that Mandy must never learn the truth about Felicia. John’s final, haunting question lingers: “Will anyone ever?” The film closes with a blend of supernatural dread and tense human drama, as memory, guilt, and the price of forbidden bargains collide along the coast.
