A series of arson claims their first victim: the lawyer Claudia von Brück is found dead in her burned-out office. Casstorff takes up the investigation with his team - and quickly realizes that the dead family lawyer was anything but undisputed. She was known for denying divorced men access to their children. But things are also crumbling behind the facade in the private environment of the dead: Casstorff determines that the daughter, Mechthild von Brück, had an affair with the partner of the murdered woman. More fires are set, but there is still no trace of the identity of the arsonist. A comparison of the firefighters' duty times does not match the times of the crime.
Casstorff suspects that the murderer took advantage of the series of fires to blame the arsonist for the crime. The investigation is now concentrating on the field of "divorced fathers" who cannot cope with being allowed to see their children for only a few hours a year. In fact, the suspicion of the ex-husband of a fire brigade employee comes to a head. But the murderer has not yet been found...