Dr. Ezekiel Malak, a hospital psychiatrist turned serial killer, is prowling for new victims in Chicago. Bex and the team work to find a method to his madness in a desperate bid to get ahead of him until Malak makes a move no one saw coming.

Arlo Brandt, a hoarder-turned-serial killer, emerges from the Pit with newly found purpose. As Arlo hunts for innocent victims, Bex and the team must get inside a deranged mind.

Bex and the team race to catch Mark Marsden, known as the Widower, a handsome and charming serial killer who murdered three of his wives in cold blood. Everything changes when Mark decides to take a new bride.