Those who Kill (Den som dræber) is based on an original idea by best-selling Danish novelist Elsebeth Egholm. It follows the inquiries of a special unit at Copenhagen's police force, consisting of detective inspector Katrina Ries Jensen (Laura Bach) and forensic psychiatrist Thomas Schaeffer (Jakob Cedergren). The pair specialise in serial killers that do not fit within traditional behavioural patterns.
Detective Katrine Ries Jensen and legal psychiatrist Thomas Schaeffer form a special unit at the Copenhagen Police investigating serial killings. A case from Schaeffer's past crops up. As a young psychologist, he held back from sending a patient, who was manically drawing the details of a traffic accident, to a secure hospital. Now these bloody scenes resurface.