Three people, the Lakhanis, an Indian couple, and an employee are shot dead by a long range sniper on a garage forecourt - a seemingly motiveless crime. Ten miles away another victim, profoundly deaf Hannah Smithson, is also shot, though her boyfriend's brother Chris, targeted with her, survives but is unable to help with any information. Inspector Jane De Freitas, on the rebound from an affair with colleague Robert Drake, calls in the pathology team but with the sniper at large and shooting indiscriminately Thomas is concerned for ex-wife Julia and their daughter Rosie, now living with former drug user Conrad Devenish. After a fifth victim, Martin Cross,a charity worker at a school is shot the killer rings Jane to tell her that he is unstoppable.

Whilst the sniper claims another body, a French lorry driver, there are fears that he may next target a school and Thomas rushes to ensure his daughter's safety. Drake calls a public meeting to pass on police progress, whereat Martin Cross's brother Ian praises him. Nikki however believes that Cross may have been the only intended victim with the others slaughtered to give the impression of a serial killer. Jack learns that Cross regularly assaulted his wife and teen-age son Craig, who hated his father, and Craig has bullets in his bedroom. Nikki and Jane now feel that Craig was working in tandem with the murderer but when the sniper strikes again Craig is standing next to the victim. They start to wonder if Martin Cross was the only person the sniper wanted out of the way and how many were working with the killer.

Nikki and Jack are called to a tube station where a homeless ex-soldier has fallen under the wheels of a subway train. Leaving the station hotel receptionist Lana Sutherland meets another homeless man, Owen Hanmore, whom she invites to stay with her, becoming his lover. Meanwhile a series of murders occurs with no visible link, beyond the fact that all the victims had used the same tube station.

Whilst fibres under the nails of the latest victim provide a link the the St Jude's homeless hostel Lana is interviewed as a formality and states that Owen Hanmore was outside the tube station at the time of the first death and must thus be innocent. Clarissa, however, finds evidence of Lana's prints on the victim's phone and Lana and Hanmore are both increasingly under suspicion as they locate Lana's child and attempt to kidnap him. The child will provide a link to the murders whilst Nikki helps Luke to come to terms with his own past.

Little Lizzie Craddock goes missing after social worker Louise Dillon has unsuccessfully applied for a care order given her father Johnny's violence. At the same time suspected paedophile Dale Barge is murdered and pictures of Lizzie are found at his flat. Young Kevin Garvey leaves care but goes to stay with his grandparents, rather than inadequate mother Niamh and stepfather Daniel, whom he blames for himself and his sisters going into care. Then Daniel is found dead.

Johnny is arrested for Dale Barge's murder but Lizzie is still missing. Evidence suggests that Kevin was present at the car where his step-father was murdered but he seems unaware of the death when he asks his sisters to run away with him and receives some shocking news from them. Lizzie's story ends well but after Kevin's grandfather Sean Patrick is also killed a terrible family secret is exposed, leading to the solution of the murders.

A shootout at a City hotel leaves young Ukrainian nanny Sofia Teplov dead, along with an unknown hitman. The Russian oligarch target Maksim Bazhanov narrowly escapes.

A young woman working for the Doshi property moguls, Amy Greenwood, is found dead in Maksim Bazhanov's apartment, and Maksim is discovered to have been in a relationship with Yasmin Doshi.

Whilst cage-fighting Jack takes on young Dean Fallon, drug dealer and son of career criminal Terry Fallon. When policeman Sam Honeywell's corpse is discovered in his burnt out car Dean is the main suspect after Honeywell had arrested him but is released for lack of evidence. Sam's colleague Carl Parry is then arrested when it is made known that Carl's wife Kate was having an affair with the dead man. After Dean has fallen out with his friend Jason Simons over Dean's girlfriend Tess Hughes Tess finds drugs hidden in her father Stan's garage, which she takes to Jason. Soon afterwards he too is killed.

Following Simons' death he is revealed to have been an undercover policeman infiltrating the Fallons' drug dealing empire. Tess questions her father and is shocked to learn that he is part of the gang before Stan gets a visit from Fallon's lawyer telling him to say nothing. There will be another death and a shoot-out before the killer is finally exposed.