A bomb explodes on a lively square and five people die. Detective Helen Dorn is one of the injured and is admitted to the hospital suffering from an acoustic trauma. The bomb explosion was a terrorist attack. The claim of responsibility video was found on the internet, so the perpetrator can be identified. It is the Muslim convert Ron Keller. During the seizure of the special police force SEK, Ron Keller is shot dead. The case seems to be solved: a psychologically disturbed assassin, non-selective killing, and quick arrest. However, Helen Dorn does not believe in this simple solution. She suspects Adrian, the man with whom she had a one night stand and who lured Helen to the square where the bomb explosion happened. Helen interferes in the investigation of her colleague Renko. She does her own research on the case and finds out that Khalid, a Lebanese drug dealer and convicted murderer, had broken out of the prison at the evening of the attack.