It all begins with a call to the police. A sixteen-year-old boy, Roger Eriksson, has gone missing. A search is organised and a group of young scouts makes an awful discovery in a marsh: Roger is dead, his heart removed.
At the same time, Sebastian Bergman, psychologist criminal profiler and one of Sweden's top experts on serial killers, is in Roger's home town dealing with family matters. Sebastian has become numb to life since the death of his wife and daughter and uses sex to escape the memories of what he's lost. But CID - which has taken over the case - needs his help.
Sebastian is drawn into the murder investigation, and what he lacks in social skills he makes up for in psychological insights as he exposes numerous betrayals and secrets - including his own.