Thomas and Bisgaard try to keep Catherine calm after Molbeck is attacked; Catherine and Thomas face their greatest foes.

As Catherine comes to terms with the death of her mother, Thomas struggles to keep her under his control. The killer who is abducting people, continues to abduct couples.

Thomas becomes obsessed about an ominous letter that puts his career and family in serious jeopardy. Catherine works to overcome a personal loss.

Catherine takes on a unlikely role when she looks at Thomas' profile and the killer strikes another family.

Catherine dives into a new case to distract herself from the revelation she heard from Thomas regarding her mother's knowledge. Meanwhile, Thomas ventures too deeply into the mind of a killer.

Thomas' decision to stop working on active cases causes Catherine to investigate his past, leading her to an unexpected family history. Catherine takes Thomas to the scene of her childhood trauma where she finally reveals all the details that still haunt her.

Catherine is forced go to Howard for more information on the case, while Thomas has a real conversation with John about getting inside the minds of murderers. Using Thomas' narrowing profile, Catherine closes in on the killer.

As the killing escalates, Catherine uses the investigation of the two victims to push Thomas to research her allegations further.

While Catherine waits to be cleared for duty by the D.A.'s office, and Thomas secretly investigates Catherine's past, a brutal murder and a John Doe suicide are discovered.

Detective Catherine Jensen teams with college professor Thomas Schaeffer to catch a serial killer. Both have troubled histories, and, although brilliant, their flaws may outweigh the positives as they try to track down the killer before he strikes again.