It's Valentine's Day, and a dispute between rival gangs leaves a teenage girl dead. Detective Inspector Charlie Resnick, nearing retirement, is hauled back to the front line to help deal with the fallout. But when the dead girl's father seeks to lay the blame on Resnick's partner, DI Lynn Kellogg, Resnick finds the line between the personal and the professional dangerously blurred. Meanwhile, the Serious and Organised Crime Agency starts to show a keen interest in one of Kellogg's murder cases-a case the agency is convinced is linked to international gun running and people trafficking. Soon Kellogg is drawn into a web of deceit and betrayal that puts both her and Resnick in mortal danger.