Detective William Wisting makes a terrifying discovery: a corpse among the spruces at a Norwegian Christmas tree farm is connected to a wanted American serial killer.

Aided by FBI agents Maggie and John, Wisting tracks American serial killer Robert Godwin to a remote farm, but will they manage to keep their mission secret from the press before Godwin bolts?

Wisting and the FBI suspect serial killer Godwin could be linked to twelve other missing person cases in Norway. Convicted killer Vidar Haglund is released from prison after 17 years and comes to confront Wisting.

Line's obsession with the Viggo case leads to a fight with her father Wisting. With the press hot on their heels, Wisting and the FBI discovers more corps, as pressure mounts to catch the serial killer.

The Viggo and Godwin case cross paths and the hunt for the serial killer intensifies as Wisting's worst nightmare becomes a reality.

Just as Wisting is hailed a national hero for solving The Caveman case, he faces accusations of evidence tampering in a previous murder case, leading to Vidar Haglund's potentially wrongful conviction. Line tries to keep her father out of the headlines, by chasing a news story on a recent murder.

Suspended detective Wisting resorts to desperate measures to prove his innocence, while Internal Affairs puts his police department under intense scrutiny. Benjamin searches for suspects in Linnea's disappearance.

Wisting and former colleague Robekk join forces, but will they figure out who was behind the evidence tampering? When Line uncovers a mysterious videotape connected to her father's case, clues point to Linnea's abduction.