On her first day in the new role, Annika and the team are called in to solve the murder of a man found in the Clyde, a harpoon piercing his head. The investigation leads them to the victim's struggling boat business, where not everything is above board.
When a body is found on a boat in the Clyde, the case takes the team to the Isle of Bute. Evidence points to a jilted lover, but a darker secret emerges as the team investigate.
When a phone with a brutal drowning recorded on it is handed in to MHU headquarters, the pressure is on for Annika and the team to track down the murderer.
When Morgan starts working at a remote Scottish eco-resort, Annika's trip to visit her is interrupted when a local builder employed by the resort turns up dead in a nearby stream.