The team is called to a drive-by shooting outside a London nightclub. They arrive to a scene of carnage with several people dead, or dying.

With the murder of the club manager, the pathologists also determine that the club owner shot his own girlfriend, likely by accident. They also identify an unlikely suspect in the shooting of the club manager. Harry and Nikki confront Leo over his abusive and unprofessional behavior.

Following the suicide of colleague Lizzie Fraser, who he believes was scapegoated by police for a wrong decision, Leo comes to work in an angry, bitter mood. DI Connie James brings Leo, Harry and Nikki in following the brutal slaying of ex-SAS soldier Mick Francis, his daughter Jessie, and her young son Luke at their farm shop during a robbery. Harry establishes a good rapport with the pregnant Connie but then Superintendent Byrne links the murders to that of Lizzie's sister Mary twelve years earlier and to several other unsolved murders in the intervening years. Byrne believes the killer is a drug-addicted woman known as the Wraith, working with a male accomplice. However unknown to him a hooded white boy who was at the shop would seem to fit the bill.

An eye witness account and identification of a car links a youth called Lee Ness to the farm shop murders but he claims not to know the Wraith. Tom Byrne,recently widowed,and Nikki,who has just lost her father,develop a rapport whilst interviewing the parents of another supposed victim of the Wraith,who have their own views on the murderer's identity. A discrepancy in the findings of the Wraith's DNA at different crime scenes leads Harry to take samples from a rival laboratory. The result reveals an elaborately plotted revenge scenario to punish the police for the deaths of Mary and Lizzie.