In New York, the boy Cameron lives with his Dutch mother Lindsey that is divorced from his alcoholic father Dan. One night, Cameron overhears a noise in the kitchen and is attacked by a homeless woman: however he kills the woman, breaking her neck. The Vatican representative Camilla summons the scientist Dr. Ember to help the boy that is possessed and the exorcism is not effective. Dr. Ember has the ability to enter in the mind of people possessed by demons and bring them back to reality in a dangerous procedure with the support of his team composed by Oliver and Riley. When Dr. Ember visits Cameron, he realizes that the boy is possessed by the insidious demon Maggie, who killed his wife and son in a car accident. Will Dr. Ember succeed in destroying Maggie and saving Cameron?