Valentine's day. A dispute between rival gangs results in one teenage girl left dead, another injured, and a police officer caught in the crossfire. Detective Inspector Charlie Resnick is recalled to the front line. But the dead girl's father seeks to lay the blame on DI Lynn Kellogg, his colleague and partner, and for Resnick the line between personal and professional is dangerously blurred. Meanwhile, a murder case in which Kellogg is the chief investigating officer has stalled. A witness is threatened, and another is missing. But then SOCA - the Serious and Organised Crime Agency - becomes involved, suspecting links to international gunrunning and people trafficking. Lynn Kellogg is drawn into a web of deceit and betrayal that puts both her and Resnick in mortal danger.