Where does science end and the supernatural begin? That's the mysterious—and dangerous—line explored by skeptical psychologist Kristen Bouchard when she teams up with priest-in-training David Acosta to explore the evil humanity is capable of. Together, they dive into the Catholic Church's files of occult phenomena to bring them to rational conclusions...or attempt to. Angel sightings, demonic possessions, prophecies and conspiracies test their faiths and push them to their limits as they learn that the world's darkness may run deeper than they ever thought possible.

In season two, Kristen struggles with her darker nature after killing a man. David suffers temptation as he gets closer to his ordination, and Ben is visited by night terrors that prey on his greatest fears.

Season three begins moments after the end of season two: when a newly ordained David and Kristen kiss. The two not only have to navigate this fraught new reality, but contend with David’s involvement with “the entity,” an espionage unit within the Catholic church. Meanwhile, Ben finds his brain breaking from their unsolved cases and turns to his sister for help.

Kristen, David and Ben continue to assess cases while Leland attempts to lure Kristen into raising the baby antichrist conceived with her ovum, culminating in one last confrontation with Leland and the 60 families that make up Evil in the modern world.