Something is wrong in the Rance household. Angela Rance suspects demonic possession and enlists the help of two priests: the progressive, but naive Father Tomas Ortega and the broken holy warrior, Father Marcus Keane. Together they will be drawn into a nightmare beyond imagination.

When Bishop Egan denies Tomas permission to perform the exorcism on Angela's daughter, Father Marcus breaks out of Saint Aquinas and joins forces with Tomas, though he urges him to get his ex, Jessica, out of his life and heart. The Rance family's relationship with the demon deepens and when Marcus catches Angela stealing holy water, he instructs her on how to use it. On Chicago's south side, a series of bizarre ritual killings begin taking place.

Kat struggles to confront the realization that her friend, Julia, is dead. Shopping for a dress to wear to Julia’s memorial service, Casey is given a sexy, expensive and slightly inappropriate dress by a salesman at the store. Seeking permission to conduct an exorcism, Marcus and Tomas take footage from the Rance home to papal emissaries, only to be met with shocking news that will change Marcus' life forever

Angela grows restless as her daughter's condition continues to deteriorate, and the demon turns its attention toward innocent victims. While Father Tomas is paid a visit by a familiar face from his past, Marcus journeys to an unexpected destination and receives guidance from a most unlikely source. With time quickly running out, the two priests must decide whether to defy the church by performing an unsanctioned exorcism.

The exorcism begins; Father Tomas and Father Marcus engage the demon in spiritual welfare, but the demon has a few secrets of its own, as the manipulations begin to drive a wedge between the Rance family.

The Rance family is engulfed in a firestorm of publicity; Father Tomas finds himself unexpectedly thrusted into the public spotlight, as his search leads him into a terrifying underbelly of the city.

Casey's disappearance takes a toll on her family; Father Marcus asks for assistance from Mother Bernadette, while dealing with the fallout from the public reveal of Casey's possession; Father Bennett's investigations leads him into danger.

Tomas, Marcus and Mother Bernadette race against time to defeat the demon, and the Rance family find themselves drawn into the conflict.

On the eve of Pope Sebastian's visit to Chicago, Marcus and his companions race to avert a potential tragedy. Tomas is offered a life-changing opportunity, but will the sins of the past endanger his future within the church? Meanwhile, as the Rance family attempts to recover from their most recent ordeal, a new problem threatens to tear them apart.

Forty years ago, the demon was denied its prize. Now it will stop at nothing to destroy Angela Rance and her family.

Six months after leaving Chicago, Father Tomas and Marcus Keane's travels lead them to a troubled young woman in rural Montana. On a secluded private island off the coast of Seattle, Andy Kim runs a group home for at-risk foster children, whose lives are disrupted when the state sends a social worker.

Tomas and Marcus attempt to finish Cindy's exorcism and escape the wrath of her family. Rose conducts her inspection of Andy Kim's household.

Marcus and Tomas travel to Seattle where they find a young girl targeted by a force of pure evil. Meanwhile, Father Bennett tracks down a rogue church operative named Mouse who is waging a one-woman crusade against the demonic conspiracy.

Andy's foster home receives a surprising new addition as he confronts the strange incidents occurring on the island. Meanwhile, Bennett's uneasy partnership with the enigmatic Mouse takes a dark turn.

As Tomas and Marcus continue to investigate the strange incidents at the foster home, the demon finally makes its presence known. Meanwhile, Andy and Rose take the children on an overnight camping trip, setting them on a collision course with the supernatural presence on the island.

A visit to the foster home carries deadly consequences, as Marcus and Father Tomas attempt to draw the demon out of hiding. Rose finds herself the target of the demon's wrath. And no one suspects that a new danger may be lurking in the woods, waiting for its moment to strike. Meanwhile, Father Bennett and Mouse take the fight directly to the conspiracy as they attempt to hunt down an old adversary.

As the exorcism begins, the fate of the foster home hangs in the balance. This is an adversary unlike anything Marcus and Tomas have ever faced, and in order to save this family, the two of them must journey into the mouth of madness itself.

As Father Bennett and Mouse head west to rendezvous with Marcus and Tomas, new details about Mouse's tragic past comes to light. With time running out to finish the exorcism, one of the foster children is faced with a difficult choice. But the demon has other plans.

As the exorcism reaches a critical juncture, Tomas engages the demon in a desperate battle to save Andy's soul. Meanwhile, Marcus and Rose attempt to get the foster children off the island, but the demon has other plans. As the storm of the century descends upon the island, salvation may come from an unlikely source.

Everything has led to this moment. As one priest fights for his life in the hospital, another is forced to confront the ghosts of his past. With time running out to save Andy's life, one of the exorcists must make the ultimate sacrifice.