When a nun in a remote convent claims immaculate conception, the Vatican sends a team of priests to investigate, concerned about an ancient prophecy that a woman will give birth to twin boys: one the Messiah, the other the Anti-Christ.

Elle a student, becomes obsessed with Katie, the heroine of a novel she's just finished reading. When Elle, battling depression, becomes convinced that Katie is actually a human being, it sets her on a reckless and terrifying course.