The hardened Swedish detective Engstrom has seen many dead bodies in his professional life. So he is not shocked by the brutal murder of a schoolgirl that he has to solve together with his colleague Erik Vik in the north of Norway. Instead, he is troubled by the incessant brightness of the midnight sun, which prevents him from sleeping. Nevertheless, Engstrom manages to set a trap for the murderer, but he escapes. During the pursuit in the dense fog, Engstrom accidentally shoots his partner Vik. On the spur of the moment, he falsifies the evidence and creates the impression that Vik has also fallen victim to the killer. The police believe him, only his colleague Hilde Hagen has doubts. Meanwhile, a classmate of the first victim has put Engstrom on the trail of the writer Jon Holt. He openly admits to the detective that he is the perpetrator - because he believes he has him in his hands. After all, he saw Engstrom shoot his partner. So Engstrom tries to protect Holt from the police in order to save his own skin. But the confrontation with the killer is inevitable, as is the confrontation with Hilde Hagen, who is getting closer and closer to the truth about Vik's death.