Devil Inside, The

In 1989, emergency responders received a 911 call from Maria Rossi, confessing that she had brutally killed three people. 20 years later, her daughter, Isabella 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. She tries to determine if her mother is mentally ill or demonically possessed. When she recruits two young exorcists to cure her mother using unconventional methods combining 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.