Detective Inspector Annika Strandhed (Nicola Walker) has returned to Glasgow to head up the Marine Homicide Unit, where she is tasked with solving the puzzling crimes and unexplained murders that wash up in Scotland’s waters. Annika takes the audience into her confidence by speaking directly to them, sharing her wry observations on the case and her life, as she balances solving cases, managing a new team, and raising a brilliant yet complex teenage daughter.

Intuitive and instinctive, Annika has a weakness for using literary and historical references to help solve her crimes, an enthusiasm that her team definitely doesn't share, but which is often the thing that unlocks the case. The team’s cases take them from the depths of Glasgow’s Clyde River to the Isle of Bute and picturesque Loch Katrine as they solve a new crime each episode, juxtaposing Scotland’s stunning landscapes and urban beauty against the horrific realities of the murders her team must solve.