Bernd Eckermann, head of HR at a well-known security company, is found shot dead in the underground car park where he works. Internal company investigations point the way to Volker Kubitzki, a bodyguard who was recently dismissed by Eckermann without notice. However, he has an alibi. Casstorff also investigates the victim's family and finds that his relationship with his wife and son was strained. But then the ballistics experts found another hot lead: the murder weapon belongs to Martin Schröder, an ex-soldier. However, he explains that the gun was stolen when his car was broken into a year ago. Shortly thereafter, the psychologist Reinhardt Mackenrodt was shot. And this according to the same model as the head of HR Eckermann.
Ballistics confirms both men were shot with the same gun. The investigators are feverishly looking for a connection between the murder victims. Casstorff finds out that both Eckermann, then still a major, and Mackenrodt, in his capacity as a military psychologist, were jointly involved in a foreign mission in Kosovo. Mackenrodt treated the soldiers traumatized by the war. They come across an unstable ex-soldier who Mackenrodt has rejected as a patient. When Casstorff puts pressure on him, he runs amok. But in this case, too, the devil is in the detail - a detail that the investigators initially did not attach any importance to. Once again the trail leads to Martin Schröder...