Mike Kovak (Colin O'Donoghue) is a seminary student from a funeral family, but he can never find any faith in his heart. By chance, Mike was sent to the Vatican to participate in an exorcist training course. He was still skeptical about God, let alone the mysterious exorcism ritual. Mike debated with the instructor from a scientific perspective. On the recommendation of the teacher, he went to visit Father Lucas Trevan (Anthony Hopkins), who was famous for exorcism. Although he personally experienced the exorcism ritual of Father Lucas, he still did not believe in the existence of the devil until a series of incredible things happened to him, and Mike's soul was really shaken... Adapted from Matt Baglio's novel "Ritual: The Making of a Modern Exorcist", the story is inspired by real events.