"Mordufer" is set in the border triangle on the northern shore of Lake Constance and combines the investigative work of the criminal investigation department and customs. The story centers on two dissimilar women: Doro Beitinger, in her early 40s, returns to her job after several years of caring for her family, children, and sick mother. Her new boss at the police department, Chiara Locatelli, is in her late 20s, ambitious, and comes from an Italian family background. Two women from different generations, with different lifestyles, who quickly realize that they work perfectly together as a team and can even solve seemingly unsolvable cases. Due to the border location, the two regularly work with their colleagues from customs, represented by customs officer Florian Jäger and senior customs inspector Nico Arnold.