Inspired by the actual files of Father Gabriele Amorth, Chief Exorcist of the Vatican, this film follows Amorth as he investigates a young boy's terrifying possession and ends up uncovering a centuries-old conspiracy the Vatican has desperately tried to keep hidden.

When an injury ends his amateur boxing career, Stuart Long moves to Los Angeles to find money and fame. While scraping by as a supermarket clerk, he meets Carmen, a Sunday school teacher who seems immune to his bad-boy charm. Determined to win her over, the longtime agnostic starts going to church to impress her. However, a motorcycle accident leaves him wondering if he can use his second chance to help others, leading to the surprising realization...