At Hillsdon Army base,a training camp for soldiers fighting in Afghanistan,young soldier Mark Blakefield is still recovering from the death in action of his friend Danny Ferris and argues with Lieutenant Lockfield,who was having an affair with Danny's girl-friend 'Cats' Felton,a fact which Lockfield's wife Claire has also discovered. Cats' body is pulled from the river some time after she was talking to the lieutenant and Nikki suspects foul play. Then Lockfield is shot,an apparent suicide,but Harry,accompanying Inspector Suzy Harte to the base,finds from the post mortem result that the man was murdered.

Nikki links Cats to the Lockfords via her phone and,at her flat,sees photos of her with her boy-friend Danny,whose father identifies her corpse. The police catch a man skulking at her flat,Dennis Croft,a former soldier cashiered for drug peddling who says there was a cover-up over Danny's death. At the request of Danny's parents a further post mortem is carried out,ultimately proving that he was killed by 'friendly fire'.Consequently it transpires that Lockford was not seeing Cats for sex but seeing her right financially. CCTV evidence shows that Cats' death was due to a bizarre accident but who killed the young lieutenant and why?

When teacher Lucy Chatham is abducted Nikki and Jack help police officers Andy Steemson and Karen Wretzy investigate the circumstances of her disappearance whilst Thomas assists abrasive DS Maureen Steele when ex-addict Tina Lunt is murdered. Doctor's daughter Jessica Timpson saw a car outside her house near the spot where Lucy was taken and her parents Nick and Ellie fear it may belong to Ellie's brother Alec Porter. Tina's death points to criminal boyfriend Wesley Beale whilst Lucy's sister's boyfriend Jasper Lampton is the key suspect when Lucy, his secret lover, is found dead. Forensic evidence suggests that both women were killed by the same man. Then Beale is murdered.

Ex-drug user Jasper is hauled in by Steemson for killing Beale, who had been his supplier but released again whilst Ellie confides her fear to Nick that Jessica is covering for Alec, whom he believes to be the murderer. Then Clarissa finds a link between Alec and a twenty year old crime in Brighton for which he was acquitted. As a result he goes on the run and Ellie finds herself in danger from an unexpected source before the multiple killer is caught.