A friendship forged between James and Tully in a small Scottish town in 1986. One weekend, they make a vow to each other to go at life differently. But then, 30 years on, half a life away, the phone rings. Tully has the worst kind of news.

The sharp, witty and enigmatic DI Annika Strandhed, as she heads up a new specialist Marine Homicide Unit (MHU) that is tasked with investigating the unexplained, brutal, and seemingly unfathomable murders.