This thriller is set in Stockholm, Sweden, where Detective Superintendent Janet Kielberg leads a murder investigation into the body of an abused little boy found in a park. As the detective deals with an indifferent prosecutor and a bureaucratic police force, the discovery of two more dismembered children confirms the existence of a serial killer. When Kielberg seeks help from therapist Sofia Zetterlund, the women's personal and professional lives become intertwined as they learn that these murders are clear evidence of an insidious evil in Swedish society.