When Angela Rance suspects demonic possession at her home, she enlists help from two priests, the progressive Father Tomas Ortega, and a broken holy warrior, Father Marcus Keane.

Tomas is denied permission to perform an exorcism on Angela's daughter, prompting Father Marcus to break out of Saint Aquinas to join forces with him; the Rance family's relationship with the demon advances.

Kat struggles to face the reality that Julia is dead; Casey is given a slightly inappropriate dress to wear at Julia's memorial service; Marcus and Tomas present footage of the Rance home to papal emissaries to get permission to conduct an exorcism.

Angela's distress increases as her daughter's condition worsens; the demon focuses on innocent victims; Father Thomas encounters a face from his past; Marcus gets unexpected guidance; the priests must decide whether to defy the church.

The storm of the century descends on Chicago as Father Tomas and Marcus battle the demon in spiritual warfare; the demon's control begins to divide members of the Rance family.

As Casey's story continues to make national headlines, Father Tomas finds himself unexpectedly thrust into the spotlight.