Michael Kovak, a seminary student struggling with his faith, decides to attend exorcism school in the Vatican as a way to address his skepticism. Though he is initially doubtful and considers leaving the priesthood, a mentor, Father Matthew, encourages him to meet Father Lucas, an experienced exorcist known for his unconventional methods. Michael travels to Italy, where he is introduced to the disturbing and mysterious world of exorcisms. He witnesses Father Lucas performing exorcisms on several individuals, all while maintaining a pragmatic and often humorous demeanor. Despite this, Michael remains doubtful and looks to rational explanations for the phenomena he witnesses.

As Michael continues to assist Father Lucas, the boundary between psychological disorders and demonic possession becomes increasingly blurred. The experiences play on Michael’s deep-seated fears and unresolved trauma, challenging his skepticism. He grapples with disturbing cases that test his courage and beliefs, all leading to a pivotal confrontation that forces him to confront his own demons. This journey of faith, doubt, and revelation unfolds against the backdrop of ancient rituals and modern skepticism, culminating in a gripping confrontation that drastically alters Michael's outlook on life and faith.