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A forensic psychiatrist discovers that all but one of her patient's multiple personalities are murder victims. She will have to find out what's happening before her time is finished.

After the death of her husband, Dr. Cara Harding's faith in God has been shaken, but not her belief in science. In an attempt to get her more open to accepting unexplainable psychiatric theories, her father introduces her to Adam, a patient with multiple personalities who also takes on some of the physical characteristics of his other personalities. But Cara quickly discovers that his other personalities were murder victims and the more she finds out about Adam and his past, the closer she and her loved ones are to becoming murder victims themselves.—napierslogs

Dr. Caroline Jessup does not believe in multiple personality disorder. Her father Dr. Harding challenges her beliefs by introducing her to a patient of his, who seemingly disproves that. She first meets David Bernberg in a wheelchair and after a series of questions demands to know why her father has asked her to meet him. She is later introduced to Adam Saber, and Wesley Crite. All the people whom this patient claims to be have already died. She later finds that he is really a doomed faith healer Reverand Christian Moore who was punished by the mountain people for his hypocrisy. He must not harvest the souls of the faithless, and Caroline must attempt to stop him from collecting her daughter's soul.

As Dr. Cara Harding (Julianne Moore), a psychologist, and her husband walk home from church on Christmas Eve, he is attacked and killed by unknown suspects.

Trying to get her to return to the world, her father (Jeffrey DeMunn) introduces her to Adam (Jonathan Rhys Meyers), a patient suspected to have multiple personality disorder. The father hopes to convince her to accept unexplainable psychiatric theories. Adam takes on seemingly impossible physical characteristics of his other personalities.

Cara's father at first tells Harding about only one of Adam's personalities, David Burnberg. She learns that David, a personality who needs a wheelchair, was a real person who became a paraplegic and was murdered long ago. Cara visits David's mother and tells her about Adam. David's mother, who is highly religious, agrees to meet Adam to help Cara cure him. Adam, as David, reveals to Mrs. Burnberg details that are private to David. She tells Adam he is evil and leaves in distress.

Adam becomes more aggressive to others, including Cara, and reveals more of his personalities. One of these is Wes, a metal band singer and Satanist suspected to have committed suicide. Thinking Adam created the personalities as escapism, Cara visits his home and finds it filthy, run-down, and full of devil worship objects. She also finds a decomposing body in the bathtub. After calling the police, Cara goes to pick up her daughter Sammy from school. Adam is with Sammy in the personality of a family friend. He questions Sammy about her faith in God, and Sammy says she does not believe anymore, because her dad was murdered. Adam is arrested and questioned about the body in his house.

Cara revisits Mrs. Bernburg, who directs Cara to a witch doctor known as 'Granny' in the witch mountains. After a brief meeting, Granny sends Cara away. Cara sneaks back after hearing screams and sees Granny cutting open an old man, sucking out his soul, and blowing it into a container with a strange symbol on it. Granny takes a cancerous lump out of his body and sews him up before blowing the soul back into him. The old man wakes up seemingly fine.

The witch doctor turns and asks Cara if she still believes only in science. Cara recalls that Adam asks about people's faiths when he meets them. She listens to two voice messages on her phone. One is from her brother, who is looking after Sammy. He tells Cara an old man may have answers for her relating to Adam.

Cara visits the man, who tells a story from his childhood while showing Cara a silent home video recorded by his father. Long ago a priest came to his town to teach about God, though he did not believe. The priest said witchcraft and pagan rituals were not needed and that people could be healed through faith. Influenza broke out in the town, but its people believed in the priest. When they discovered the priest was a nonbeliever who had inoculated his two daughters against the flu but allowed the townspeople to die, they murdered his daughters. Granny sucked out his soul and blew it into the air before stuffing his orifices with mud so his soul could not return. She cursed his body to be a shelter to the faithless.

The police tell Cara that they released 'Adam' to her father and that the body in his bathtub was the real Adam who had owned the home. Cara looks up at the projector screen and sees 'Adam' in the midst of the influenza epidemic. He is the faithless priest from decades ago. Cara calls her dad, realizing 'Adam' is going to kill him. She listens helplessly as the murder takes place, and Adam sucks out her father's soul.

Cara calls her brother about her discoveries. He tells her Sammy is growing sick just as her family friend and father had been, and has a strange symbol burnt onto her back. Cara asks him to take Sammy to Granny. 'Adam' shows up as Cara's father, but Stevie hides in the bathroom. Her brother is injured by accident. Cara tells Sammy to put the call on speaker not knowing its her father's soul in possession and demands to speak to David. As 'Adam' transforms back into David, he collapses, as David needs a wheelchair. Cara's brother and daughter escape.

After joining them, Cara sees the symbol on Sammy is the same as the one on the witch doctor's container. Granny says she cannot help, as Sammy has already given up on God, but that Sammy will be sheltered with the other faithless souls. 'Adam' knocks out Cara's brother and overpowers Cara. He sucks out Sammy's soul and changes into her personality, revealing he does not have DID, but is the shelter for the spirits of people who abandoned their faith in God.

'Adam' as Sammy lets Cara cradle him. She strangles him and impales his neck with a root protruding from the ground. As the faithless priest 'Adam' dies, all the souls leave his body.

Sammy's lifeless body receives her soul back. As Cara and Sammy comfort each other, Sammy hums a tune written by David, implying David's soul has gone into his body.