In the tranquil Hooksiel on the North Sea, not much has changed since former police chief Stefan Schrader from Hamburg sailed in with his sailboat "Udel" last year. Together with his new partner Helene, he is planning an extensive sailing trip through the East Frisian Wadden Sea and the canals of Holland for the upcoming summer. However, Helene, a former art history student, accidentally discovers something unusual, even incredible, in an ancient photograph. Does this relate to the strange events at the water castle Hechthausen over a hundred years ago? Everything takes an unexpected turn when outsiders get involved. A dramatic race against time begins. Ignoring the old Frisian traditions proves to be a fatal mistake, as the hardened ex-cop Schrader learns firsthand.