The year is 1740, and the Vatican is in turmoil. Grappling with a profound crisis of faith, outcast exorcist Father Franco Vieri is dispatched on a mission of grave importance - to rescue a Spanish nobleman from the clutches of the sadistic demon known as Legion. But when the exorcism goes tragically wrong, Vieri finds himself trapped in a stranger's body... and learns what horrors lie ahead when the Devil wears his face.