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

Catherine looks to glean more information from her stepfather; Catherine makes use of Thomas' profile, narrowing the search as she continues her dogged pursuit of the killer; Thomas and John discuss ways one might 'enter' a killer's mind.

Catherine distracts herself from Thomas' revelation about her mother by diving into a new case.

The killer invades another family; Thomas' profile causes Catherine to take on an unlikely role.

Thomas obsesses over an ominous letter that puts his career and family in jeopardy, while Catherine attempts to put the past behind her after a sudden personal loss.

Thomas tries to keep Catherine under control after the death of her mother proves too difficult for her to handle. A sadistic killer continues to abduct couples.

After Catherine abandons Molbeck to be attacked by the killer, Thomas and Bisgaard struggle to keep her from going off the rails. Catherine and Thomas face their greatest foes.