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.

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.