Based on a true story, The Ritual follows two priests - one questioning his faith (Stevens) and one reckoning with a troubled past (Pacino) – who must put aside their differences to save a possessed young woman through a difficult and dangerous series of exorcisms. The film is an authentic portrayal of Emma Schmidt, an American woman whose demonic possession culminated in harrowing exorcisms. Her case remains the most thoroughly documented exorcism in American history.