On a frigid January day in 2006, a gruesome discovery is made by the police in the Swedish town of Hudiksvall: 18 people have been savagely killed in a single night. The authorities suspect a deranged individual is responsible for the horrific crime. However, when judge Birgitta Roslin learns of the incident, she immediately recognizes that her grandparents, August and Britta Andrén, are among the deceased. Moreover, she discovers that nearly all the victims are somehow connected to her. Realizing that the police are pursuing the wrong leads, she embarks on her own investigation. Her quest takes her to China, where she uncovers the ruthless machinations of the ruling elite.