Season three of Evil 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.

The second season brings evil closer to home. Kristen struggles with her darker nature, while David suffers temptation as he gets closer to his ordination. Meanwhile Ben is visited by night terrors that prey on his greatest fears.