Holly Gooding, Drew Barrymore, moves from New York City to Los Angeles after being implicated in a murder. She is followed by what seems to be her evil twin, a troubling presence that haunts her every step. In Los Angeles, she spots a room for rent offered by a writer named Patrick Highsmith, George Newbern, whose curiosity about Holly quickly becomes more than just a landlord-tenant interest.
Patrick notices that something about Holly isn’t right, yet he can’t help but be drawn to her. He learns that Holly’s brother Fred is locked away in a psychiatric hospital after killing their father, and the more he digs, the more tangled the truth appears. When Patrick discovers that Holly’s mother was murdered and that Holly herself is the prime suspect, his confidence in her sanity wavers, though his growing feelings prevent him from rushing to the police. He decides to uncover the truth on his own, relying on the help of his writing partner and ex-girlfriend Elizabeth, Leslie Hope, as they piece together a labyrinth of deceit.
The mystery deepens as Patrick is attacked by a knife-wielding man who is identical to Holly’s supposedly dead father, and he follows Holly back to her family home. There, he is ambushed by Dr. Heller, Dennis Christopher a psychiatrist who appears to be the man behind the strange happenings, wearing masks and disguises that reveal a network of doppelgängers pulling the strings. Dr. Heller is revealed as the primary architect of Holly’s misfortunes, including the murder of Holly’s mother, a crime tied to a plan to seize her trust fund and inheritance by marrying Holly.
As the tension crescendos, Holly undergoes a bizarre supernatural transformation. She splits into two partially formed beings, one of which knocks the other unconscious and then kills Dr. Heller. The surviving fragment of Holly seems ready to threaten Patrick, but instead she spares him and reunites with her other half just as the police arrive, along with Elizabeth, who has been quietly piecing together the truth all along.
Patrick attends what feels like Holly’s end, a funeral that compresses fear and longing into a single moment. Yet after she is laid to rest, his nightmarish vision returns: the evil doppelgänger reappears, seductively closing in before morphing into the monstrous figure responsible for the tragedy that began this chain of events. He wakes in a hospital bed, discovering that he and Holly are both alive and recovering. As he drifts back toward sleep, Holly recalls the ordeals she endured and clutches the music box her abusive father gave her, a relic that ties the whole haunting chapter together and hints at the fragile line between memory and illusion.
