Detective William Wisting makes a terrifying discovery: A corpse has been found among the fir trees at a Norwegian Christmas tree farm, and appears to have links to a wanted American serial killer.
With the help of FBI agents Maggie and John, Wisting tracks down serial killer Robert Godwin to a remote farm, but can they keep the mission secret from the press before Godwin slips away?
Wisting and the FBI suspect that Godwin is linked to twelve other missing person cases in Norway. Meanwhile, convicted gunman Vidar Haglund escapes from prison after 17 years, and heads to confront Wisting.
Line’s obsession with the Viggo case leads to a quarrel with her father, Wisting. With the press right behind them, Wisting and the FBI discover more bodies, which adds to the pressure on them to capture the perpetrator.
The Viggo and the Godwin cases cross paths, and the pursuit of the serial killer becomes more intense as Wisting’s worst nightmare becomes a reality.
Just as Wisting is being hailed a national hero for solving the Caveman case, he is accused of falsifying evidence in a previous murder case, leading to Vidar Haglund’s potentially wrongful conviction.
Internal Affairs looks into Wisting and, following his suspension, Torunn leads an investigation into the disappearance of a young woman. Elsewhere, Line meets an old flame.
Wisting fights for his career and reputation by conducting a secret investigation into the Cecilia case. Torunn suspects that Linnea is responsible for her own disappearance, but her parents are not convinced.
Suspended Wisting resorts to desperate measures to prove his innocence, while Internal Affairs investigates his police department. Benjamin searches for suspects in connection with Linnea’s disappearance.
Wisting and colleague Robekk work together on the Cecilia case, but can they figure out who was behind the tampered evidence? Line finds a mysterious video cassette linked to her father’s case that offers new clues regarding Linnea’s abduction.