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 the body of a scientist is found in Loch Katrine, Annika is reminded of Ibsen's Enemy of the People. But with so many wanting him dead, which one did he push over the edge?