Architect Gero Albrecht is found dead in his car in a remote parking lot. Forensics show that the car’s doors had been sealed with a special kind of flammable foam and set on fire. Within seconds, a mix of toxic gases developed which Gero Albrecht could not escape. While investigators are still questioning the architect’s friends, family, and acquaintances, a second body is found: Albrecht’s partner Soenke Schmidt was also murdered – in Sweden. The circumstances on the crime scene are absolutely identical. No coincidence, for sure! Did dark schemes surrounding the two men’s construction business lead to their death? That is what Swedish colleagues of inspector Sven Herzog believe, when he travels to Sweden to coordinate investigations. An anonymous letter has been found, pointing towards bribe money paid during the last construction project the dead men were involved in. New clues surface in Wismar as well: a representative with power of attorney turns up, who had affairs with and was left by both deceased. Then there is a wife, who apparently has a relationship with her husband that is much less intimate, and one with his ex-lover that is much more intimate than she initially admits. And then there is an old unsolved case, also dealing with a mysterious fire. But where is the connection? In the end, it becomes more and more obvious to the investigators that there is one thing they must prevent no matter what: the third fire!