In 1989, emergency responders received a 9-1-1 call from Maria Rossi (Suzan Crowley) confessing that she had brutally killed three people. 20 years later, her daughter Isabella (Fernanda Andrade) seeks to understand the truth about what happened that night. She travels to the Centrino Hospital for the Criminally Insane in Italy where her mother has been locked away to determine if her mother is mentally ill or demonically possessed. When she recruits two young exorcists (Simon Quarterman and Evan Helmuth) to cure her mom using unconventional methods combining both science and religion, they come face-to-face with pure evil in the form of four powerful demons possessing Maria.
Many have been possessed by one; only one has been possessed by many.