When Nikki sees barefoot teen-ager Shannon Kelly run over by a car whilst fleeing somebody she sits with her until the ambulance arrives and later visits her in hospital,where it is clear she is frightened of a man. DS Masood tells Nikki Shannon has been sexually abused and suspects Abdul,her estranged stepfather. Shannon turns up at Nikki's and reluctantly agrees to go back to hospital. Meanwhile a gang of young Asian men are picking up and grooming white school-girls for the sex trade. They already have Shannon's friend Amy and go after two more,Hannah and Lauren. The pathologists investigate two seemingly unrelated cases - the remains of a young girl found in discarded airport luggage and a heavily tattooed man,John Dear,who died of toxic poisoning. Then a third corpse is found - that of Amy.

Through a DNA link the pathologists find that John Dear was a client of unwilling child prostitutes Shannon and the deceased Amy whilst the suitcase victim is also identified. Nikki visits Shannon in hospital and learns about the gang of abductors but the young girl is too scared to name names. Through CCTV DS Masood gets the car registration number of a visitor to Shannon and arrives at a taxi firm where Salman,a somewhat reluctant and kind-hearted gang member, works. Salman helps Hannah and Lauren escape but is killed when his taxi crashes. The three girls are returned home but will not speak about their ordeal and,with Abdul swearing revenge, Nikki must help DS Masood resolve matters. The case closed Harry announces that he is leaving to take up a professorship in New York.

Harry's work colleague Justine Thompson is murdered in her house with her daughter Gemma whilst her stepson Charlie, also attacked, lies in a coma. Baby daughter Ellie, however, is unharmed. Husband Stuart is prime suspect but he has an alibi and his grief seems genuine. The post mortem shows that Gemma was pregnant and the team learns that Justine once needed a restraining order against Stuart's brother Kevin, who was obsessed with her. Mrs Barron, the lady from next door who found the bodies, finds evidence on her son Joel's computer that Gemma and Charlie were lovers as Joel rides off to see Kevin.

After Kevin dies in a motorcycle crash Harry is surprised to see Joel keeping a vigil by Charlie's hospital bed. Whilst denying murder Joel professes that he loved Gemma was shocked that she was sleeping with Charlie. Stuart's initial alibi breaks down when CCTV footage shows Kevin, not him, at the hotel in question but he admits to an affair with Mrs Barron. The murderer is eventually exposed after a shocking betrayal is revealed, leading to an horrific reaction.