In 1980, a married woman has illicit sex with a lover while her adolescent son waits in a car outside; their lovemaking is disturbed when they think somebody is looking at them from outside the window, but it turns out to be only a snowman.

Twenty-four years later, Norwegian police inspector Harry Hole investigates a string of murders of women around Oslo.

His FBI training leads him to search for links between the cases, and he finds two of them—each victim is a married mother, and a snowman appears at every murder scene.

Further digging leads Hole and his team, including newcomer Katrine Bratt, to suspect that paternity issues with the victims’ children may be a motive for the murders.

When a chance comment triggers a random thought, he makes a vital connection that ultimately leads him to the identity of the true perpetrator.

His success in finally apprehending the killer obviates any need for a scapegoat, and Bratt, after further mental stability checks, returns to her post in Bergen.