Karen, a 38-year-old couples counselor and mother of three, has her life turned upside down when she discovers her husband's infidelity. Suddenly single, she must say good-bye to the utopian vision of the perfect nuclear family, and the professional advice she gives her clients now seem absurd. Every other weekend, the so-called "daddy weekends", are what Karen no fears most. 

When a third victim is found stabbed to death, police officers Kata and Arnar realize they're dealing with Iceland's first serial killer. As they start connecting dots, the trail leads them to a mysterious and abandoned boys' home named Valhalla, where a series of horrendous crimes occurred 35 years earlier. As the past catches up with the present, more lives are in danger.