Young detective Ria Larsen is faced with the question of how serial killer Wernicke, who is imprisoned in a psychiatric ward, instructs brutal murders on the Husum coast. The bodies in the dunes point to a copy killer. During the investigation, Ria suddenly finds herself in a race against time and in a dangerous mind game with a ritual killer who has already destroyed the life of her predecessor.

The tide washes up a slain Viking warrior on the beach in Husum: the unusual "dead body by the sea" is not a case for historians, however, but for the police and detective Ria Larsen. Marlene Tanczik plays the battered but combative investigator in the second film in the Saturday evening crime series on the first channel. Christoph Letkowski plays her partner Brandt, who believes in Ria's special abilities and is loyal to her.

Two mysterious deaths, rivalries within the Husum police team and a mysterious marine biologist who is both a witness and a suspect - Marlene Tanczik, alias Inspector Ria Larsen, faces a number of challenges in the third crime thriller in the series.