Mord in Hesel. Ostfrieslandkrimi

Lara Bosner is found strangled in her home in Hesel, East Frisia. Everything points to a sexual offense, especially since the attractive tax officer had received several obscene threatening letters beforehand. The messages were written on light blue stationery, just like in similar recent cases in Aurich and Bensersiel. Is there a connection, and has the police wrongfully imprisoned an innocent person in these cases? Or is a copycat offender trying to mislead the investigation? Dr. Josefine Brenner, a retired forensic pathologist, is assisting the local police with the investigations. It seems cursed, as soon as they have a suspect, they must remove him from the list again. And then the nightmare appears to continue: the victim's best friend receives an unmistakable handwritten message on light blue stationery...