Developmental psychologist Dr. Philip Lacan performs as a
magician at a children's party at the Zurvan Institute, a clinical psychology hospital outside
Vancouver. Angelique, a Frenchwoman who is one of his former patients and ex-wife, performs as Philip's assistant. Grace Collier, an undercover journalist investigating claims of malpractice against Philip, is exposed at the party and thrown out, an event witnessed by physician Dylan Wallace, who has volunteered at the event. Dylan gives Angelique a ride back to her apartment in the city, where she resides with her
twin sister, Annabel, who remains unseen in a closed bedroom. Angelique reveals that the following day is her and her sister's birthday. After Dylan and Angelique have a
one-night stand, Dylan goes to purchase a birthday cake in the morning. Meanwhile, a suspicious Grace, who spent the night parked outside Philip's apartment across the street, breaks in and begins investigating his office. From Philip's computer, Grace witnesses a disheveled Annabel brutally stab Dylan with knitting needles when he returns via live
security footage from inside the twins' apartment. After calling police, Grace evades Philip, who briefly returns to retrieve his cell phone, before glimpsing a bloodied Dylan reaching out of Angelique's apartment window across the street. Philip enters Angelique's apartment, where she claims she fell asleep, during which Annabel murdered Dylan. Grace leads police to Angelique's apartment but they find no evidence of a crime, as Philip has hidden Dylan's corpse behind a television set. A self-assured Grace later meets with her friend, Larry, who agrees to break into Angelique's apartment to search for evidence. Meanwhile, Grace encounters Angelique in the park, where she notices track marks on her arm, and suspects Philip is experimenting on Angelique with a novel
psychotropic drug. Larry finds Dylan's corpse inside Angelique's apartment, which he reports to Grace. He also gives Grace a cassette tape he discovered inside a dresser drawer. Grace listens to the tape in her car, finding it to be a recorded therapy session between Philip and Angelique and Annabel's mother, Sofia. It is subsequently revealed that Grace's own mother was committed to a psychiatric hospital, sparking a personal vendetta against the institute and its practices. Grace tracks one of Philip's former assistants, Dr. Mercedes Kent, and questions her about her time at Zurvan. Mercedes reveals that Sofia, an exchange student who came to Zurvan and birthed Angelique and Annabel,
conjoined twins. Sofia fled the institute with her daughters back to France, where the twins performed in circus
freak shows before being recaptured and recommitted to Zurvan. Philip observed a disturbed dynamic between Angelique and Annabel, with Angelique exhibiting complacency while Annabel exhibited violent impulses. Mercedes reveals to Grace that Annabel died of
lung failure after Philip surgically separated them, and that Angelique has since lived alone under Philip's supervision. Grace informs Larry before driving to Zurvan, where she is confronted by Philip, who incapacitates her with a sedative. In a series of
hallucinations, Grace bears witness to Annabel's psychotic state of mind, Philip's sexual affair with Angelique, and his declaration of Annabel as a psychologically "
parasitic" entity. In order to pursue his affair with Angelique, Philip performed the
surgical separation of the twins which killed Annabel; Angelique has since lived in a state of guilt, causing her to adopt elements of her dead sister's psyche. As Philip attempts to rationalize his actions, Angelique realizes that Philip manipulated her and also killed her mother. Grace, in a
dissociated state, stabs Philip to death with a large
syringe. Shortly after, Larry, who arrived at Zurvan to help Grace, is stabbed by Angelique. When Larry calls her by name, Grace corrects him, saying her name is Annabel. Angelique proceeds to cut Grace along her ribcage with a scalpel, creating a matching surgical scar the two can share. The following morning, Angelique and Grace depart Zurvan, their arms wrapped around each other. ==Cast==