Michael Kovak (Colin O'Donoghue – The Tudors) is experiencing a crisis of faith and because of this decides to leave his theological training on the eve of graduating. An accident occurs and leaves Michael questioning his chosen path so his superior Father Matthew (Toby Jones – Frost/Nixon) sends him on a special mission to The Vatican. Once there, Michael begins his training to be an Exorcist under the guide of Father Xavier (Ciaran Hinds – Miami Vice) and the unorthodox Father Lucas Trevant (Sir Anthony Hopkins – The Wolfman). Unconvinced at first, Michael reluctantly helps Father Trevant with the supposed demonic possession of a young girl under his care. But as they delve deeper into the case, Michael soon learns that his faith could be the only thing that can save him.