Forensic evidence given by Nikki contributes to the release on appeal of disturbed ex-soldier David Bennetto, charged with murdering two gay boys, one of whom he had sex with. DI Rachel Klein is not convinced of David's innocence , especially when a rent boy calling himself Byron Lee is shot dead and David's car is caught on CCTV near the murder scene. The fact that Nikki is dating Bennetto's solicitor Greg Walker makes her partial in the inspector's eyes and she is removed from the case. On the night that yet another gay youngster Charlie Masham is also shot Greg, on a date with Nikki, gets a frantic phone call from Bennetto and they go to his flat where he points a gun at them after he discovers Nikki has found his kitbag containing the murder weapons

The police surround the flat but David hands the gun over to Greg, explaining that it was his father's gun, which he had found and wanted to get rid of. Nikki is verbally abused by Charlie's father and DI Klein wants her suspended but Clarissa and Jack discover that the gun found by David did not kill Charlie and nor could he have killed Byron Lee. The pathologists work out that the real serial killer had an alarming insight into David Bennetto's background and their motive was not sexual but obsessed with having power over others. Circumstances also end Nikki's involvement with Greg Walker.

Matt is found alive after his abduction but admits that the kidnapper wanted information about an incident that happened in Africa when Helen and Ryan were there. All of the victims, including another in Florida, were murdered in the style of assassinated American presidents but Fergus has an alibi for them all though Matt learns that he has information which identify the murderer. Now the police and the pathologists must work together before Fergus is also killed.