Forensic evidence concludes that the same person killed Patrick and Pernille. As Louise and Frederik probe the link between the victims, an old gang-related double murder emerges, suggesting a potential quadruple killer.

In their search for Kim, a clue leads Louise and Frederik to Sweden. Meanwhile, Kim hides with his stepdaughter in a remote cottage. Louise and Frederik track Kim down, only to discover yet another devastating crime.

Under interrogation, Kim confesses to the old double murder and the killing of his girlfriend, but not to the murders of Patrick and Pernille. Dismantling Kim’s alibi, Louise has reason to come up with a new theory.

A revelation from Kim’s stepdaughter puts the spotlight on Kim’s old gangleader, Robin. Meanwhile, Kim is warned to keep silent, and an attack on Robin’s gang hints at an imminent gang war. Robin flees with his family.

Louise believes Robin was killed by the same murderer as the other victims, but Frederik suspects his death was a stand-alone gang murder. However, Louise convinces Frederik that a fatal car accident links the killings

With Louise's world falling apart, the case is taken over by Jacob, Frederik’s second-in-command. Jacob is determined to track down the killer, but must also contend with Louise - who soon discovers a shocking new lead.

Alongside Jacob, Louise tries to prove Gunnar’s guilt and uncover his motive. It appears that the loss of his daughter in a car accident and the driver's short sentence was the catalyst for Gunnar's murderous campaign.