Susanne Elvan met her husband Tarek, a convicted violent criminal, through a penpal portal while he was in inprisonment. The wedding took place before his release. When Susanne was found murdered, Tarek had only recently been out of prison. The case seems clear, at least for Susanne's daughter Mia, who detests her mother's easily irritable new husband. The Cologne commissioners Ballauf and Schenk start the investigation. But when assistant Norbert Jütte sees on a crime scene photo that the murderer has tied a belt over his victim's eyes, the case takes an unexpected turn: Jütte is convinced that he has dealt with the murderer before, earlier in his career, when he was doing his duty in another police department in another city. A serial perpetrator with a recurring murder ritual seems to be straggeling around in the city.