Based on the Danish TV crime series inspired by bestselling author Elsebeth Egholm, "Those Who Kill" stars Chloë Sevigny as Catherine Jensen, a brilliant police detective who tracks down serial killers. Jensen is also investigating her stepfather, who may be a serial killer, while searching for her missing brother. She enlists the help of Thomas Schaffer (James D’Arcy), a forensic psychiatrist, to help her understand the minds of serial killers, all the while luring Schaffer into her own personal investigation. Both characters possess a deep psychological understanding that connects them to the killers' victims and to the killers themselves.
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.
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.
As the killing escalates, Catherine uses the investigation of the two victims to push Thomas to research her allegations further.
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.
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 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.
Catherine takes on a unlikely role when she looks at Thomas' profile and the killer strikes another family.
Thomas becomes obsessed about an ominous letter that puts his career and family in serious jeopardy. Catherine works to overcome a personal loss.
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 and Bisgaard try to keep Catherine calm after Molbeck is attacked; Catherine and Thomas face their greatest foes.