A corpse in the dunes of Borkum presents a puzzle for Commissioner Mona Sander and her colleague Enno Moll. Was it murder? How long has the dead man been buried under the sand? Once the man's identity is established, the case really picks up speed. Suddenly, another crime occurs, and Mona Sander finds herself getting personally closer to a murder suspect. In this East Frisian idyll, there are many people who have something to hide. To uncover the perpetrator, the commissioner must solve a dark secret from the past.