In the Bay of Hohwacht, a lifeless man lies in full diving gear. Was it an accident or murder? Frida Beck and Deniz Yilmaz begin their investigation at the upscale Niendorf diving club. It turns out that the club offers illegal tours to historical wrecks. The commissioner suspects that the deceased was smuggling art treasures and had a confrontation with a competitor. However, when another dead body is found shortly thereafter, Frida realizes that she has been following a false lead.