When a 12-year-old girl is possessed by a mysterious entity, her mother seeks the help of two priests to save her.
Philip Lamont, a priest struggling with his faith, attempts to exorcise a possessed South American girl who claims to "heal the sick". However, the exorcism goes wrong and a lit candle sets fire to the girl's dress, killing her. Afterwards, Lamont is assigned by the Cardinal to investigate the death of Father Lankester Merrin, who had been killed four years earlier in the course of exorcising the Assyrian demon Pazuzu from Regan MacNeil. The Cardinal informs Lamont that Merrin is facing posthumous heresy charges because of his controversial writings as Church authorities are trying to modernize and do not want to acknowledge that Satan exists.
A woman crawls by unnoticed - on the ceiling like a fly. A long-dead killer claims victim after victim. Flames erupt, snakes slither, the ground opens and reveals a writhing pit of the damned. The evil is back.
Years before Father Lankester Merrin helped save Regan MacNeil's soul, he first encounters the demon Pazuzu in East Africa. This is the tale of Father Merrin's initial battle with Pazuzu and the rediscovery of his faith.
Father Tomas Ortega is the new face of the Catholic Church: progressive, ambitious and compassionate. He runs a small, but loyal, parish in the suburbs of Chicago. Father Marcus Keane is a modern-day Templar Knight, an orphan raised since childhood by the Vatican to wage war against its enemies. Marcus is everything Tomas is not: relentless, abrasive and utterly consumed by his mission – and he constantly butts heads with his adversary within the church, Father Bennett.
