Plot

A psychiatrist becomes obsessed with one of her young patients, who she later discovers is linked to an ancient curse.

In a series of flashbacks, confused psychiatrist Dr Elizabeth Derby recounts the terrifying story of her downfall to her best friend and colleague, Dr Daniella Upton. It all started when Elizabeth had an unannounced visit by distressed teenager Asa, who kept insisting that there's more to his abusive father than meets the eye. Genuinely concerned about the young man's mental health, Dr Derby delved deeper and deeper into the strange case of multiple personality disorder, only to drift apart from her family. And the more Elizabeth exposed herself to Asa's mysterious horrors, the more she questioned her sanity. But if the thing in Asa's mind is real, what good is science when you're suitable flesh?—Nick Riganas

Dr. Daniella Upton visits the morgue of the psychiatric hospital where she works, and the coroner shows the just arrived smashed corpse. Then she visits a cell, where the killer is locked up. She is her friend, Dr. Elizabeth "Beth" Derby, who begs her to destroy the brain of her victim. Daniella questions her and she tells the story of what happened to her. Dr. Elizabeth Derby is a psychiatrist, married with Edward "Eddie" Derby and living in a comfortable house in the suburbs. After her last session at her office, Beth is preparing to go home when a young man named Asa Waite begs to talk to her. He says that he read her book about traveling out of the body and claims that her father uses his body. When he receives a phone call from his father, he has a seizure and changes his behavior. Elizabeth believes Asa is schizophrenic and feels attracted by him. During the night, she fantasizes having sex with Asa, instead of with her husband. On the next morning, she goes to Asa's address and meets his father Ephraim Waite, who is very sick, agonizing and she helps him by giving him a pill for his cardiac problem. During the night, Elizabeth receives a phone call from Asa and drives to his house. She finds Ephraim dying and Asa asks her to not help his father, but she gives his pills for him. Asa says that they must destroy his brain; otherwise, he will possess Asa's body. But Ephraim says some words and possesses Asa's body and has sex with Elizabeth. On the next day, he possesses Elizabeth's body and has kinky sex with Eddie. Now Elizabeth learns that Asa was telling the truth. She also discovers that the only way to get rid of the evil Ephraim is killing him and destroying his brain. But the police stopped her before the brain is destroyed. Soon Daniella will find that her friend is not crazy.—Claudio Carvalho, Rio de Janeiro, Brazil

In a psychiatric hospital, Dr. Daniella Upton visits the morgue. There, the mortician dissects a corpse, the victim of a murder. Daniella visits the murderer, her friend Dr. Elizabeth Derby, who begs Daniella to destroy the corpse's brain and begins to recount her story to explain why she must do so.

Psychiatrist Elizabeth Derby lives with her husband Eddie, never being troubled by her patients. After a session with a patient, a young man visits her office and asks to talk to her; he introduces himself as Asa Waite and says that he believes that his father Ephraim is occasionally "using" his body. During the session, Asa receives a call from his father and appears to have a seizure before acting as if nothing happened, as well as behaving differently. Elizabeth is troubled by this development and that evening imagines Asa in Eddie's place while they are having sex. She goes to Asa's house, having remembered his address, and discovers Ephraim to be horribly sick, relying on pills to keep him alive; Ephraim wards Elizabeth off with a large knife after she spots a book with creatures and symbols drawn in it.

That night, Asa calls Elizabeth and she drives to his house, finding Ephraim dying on the floor; Asa refuses to let Elizabeth hand him his pills but Elizabeth defies his orders, though she cannot stop Ephraim's apparent death. Asa tells her that they must destroy Ephraim's brain because if he says an incantation a third time, he will take over Asa's body; Ephraim, revealed to be alive, utters the incantation and causes Asa to have a seizure before seemingly dying a second time. Asa, now more confident, has sex with Elizabeth and whispers an incantation in her ear which causes them to briefly switch bodies. He notices that Ephraim's body is missing, prompting him to take the knife and chase after him. Ephraim begs Elizabeth to help him as he is actually Asa in Ephraim's body but the real Ephraim, now in Asa's body, stabs him in the neck with the knife before decapitating him.

The following day, two detectives stop by the Derby residence to question Elizabeth about a fire at the Waite house, with Ephraim being labeled as a missing person. Elizabeth talks to her friend, fellow psychiatrist, Daniella Upton, about the body-switch but Daniella does not understand what she means; later, Elizabeth admits to Eddie that she has had sex with Asa. Meanwhile, Ephraim (still in Asa's body) handcuffs himself to a pole in his cellar and calls Elizabeth, reading the incantation and causing the two to switch bodies. While in Elizabeth's body, Ephraim has sex with Eddie; Elizabeth discovers piles of flesh as well as drawings of a creature in the cellar. Realizing that the next body swap will be forever, Elizabeth attempts to jump out of a window at her office but Ephraim arrives and says that she can escape if she kills him and destroys his brain. Upon distracting him, Elizabeth stabs him in the head with his knife before throwing him out of the window; realizing that he is still alive, Elizabeth runs Ephraim over repeatedly with her car before stabbing him to death. She is then apprehended by police officers.

In present day, the mutilated corpse, now revealed to be Ephraim, awakens and utters the incantation one final time, causing him to switch bodies with Elizabeth. Elizabeth in the corpse's body begins to crawl through the hospital while Ephraim decides to switch bodies with Daniella, causing the two of them to fight. In Daniella's body, Ephraim begs security guard Mace to shoot Daniella but she manages to get his gun and euthanizes Elizabeth by shooting her in the head repeatedly. The two switch back and Ephraim shoots Mace to death before continuing to fight; Daniella gets ready to stab him with a scalpel as Ephraim recites the incantation again, before they are separated by police officers. Daniella later consoles Eddie in her office as Ephraim is revealed to be in control of her body while the real Daniella is trapped inside the body of a screaming Elizabeth. (thanks to Wikipedia)