Jonas Engström and his collegue Erik Vik are sent to the northern region of Norway, above the arctic circle. They have to investigate the murder of a 17 year old girl, a murder that hasn't been seen in that region for a long time. Because the region of the murder is above the arctic circle, the sun does not set anymore. It shines, 24 houres a day.
Engström is originaly from Sweden, but had to leave Sweden for a while after he got caught in a relationship with one of the main witnesses in an other case. He joined the police force of Norway and now had to investigate this case. He is not used to a never setting sun, which causes Insomnia.
At the second day of the investigation, the police force sets up a trap to catch the murderer. It ends in a foot-chase through the mountains in heavy fog. During the chase, the suspects fires a gun at the police men which makes Engström firing back and he hits. When he walks to the men he hit, it turns out he accidently shot his collegue Vik.
A second investigation starts, due to the murder on Erik Vik, and Engström decides to pin the murder on the suspect.
Shortly after the incident, Engström tracks down a writer, Jon Holt, that must have been involved in the case. During a search through his appartment he found nothing, but the writer found out he was there. Later that night, he calls him up and tells Engström to stay away. Engström tells Holt he wants to talk to him, but Holt dissagrees. Engström still can't sleep at night.
Engström finds Holt the next morning and chases him to a cable car that goes up a mountain. In the cable car they have a conversation. Holt explains to Engström that he never intended to kill the girl. It was an accident and that they had to pin the murder to her boyfriend, 'cause he often beat her up.
Engström dissagrees at first, but then Jon tells him he saw him when he shot Vik. If Holt got caught for the murder, then he would also tell them that Engström killed Vik.
They decide to cover up both murders by pinning them on the boyfriend. Engström hides the gun in his room and finds it later during a house search. The boyfriend is imideately arrested.
Holt and Engström meet eachother one more time, because they don't trust each other. Engström still thinks that Holt should be arrested instead of the boyfriend. They have a fight that ends in a chase though old and rotten piers. Holt makes one wrong step and falls through the wooden pier, breaks his back and drops into the water. Engström walks to him and sees him when he's still alive, though he does not save him. Holt dies.
The police discover that Holt had murdered the girl, and not the boyfriend. Engström still sticks to his story that Holt killed Vik and decides to go back to Sweden.