Detective inspector Annika Strandhed has returned to Glasgow to head up the Marine Homicide Unite, 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 Intuitive and instinctive, Annika has a weakness for using literary and historical references to help solve her crimes, an enthusiasm that her team definitely doesn't share, but which is often the thing that unlocks the case.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.