Single mother Dinah Kowalska, an off duty detective constable, pursues a murder suspect through the streets of Manchester, only for him to get knocked down and killed by a bus. As a result DI Viv Deering, her outspoken superior, instructs her to withdraw her application for sergeant, the promotion going instead to her nervous colleague Joy Freers. On a visit to the morgue Dinah sees the corpse of a Downs Syndrome sufferer, the second girl with that condition to be hauled out of a river in recent weeks, and suspects a serial killer is at large. Cathy Calvert, who ...

Dinah is taken off the murder case as her involvement with Cathy has made her too subjective but Viv asks her to assist when a student is found dead in the street of an overdose and drugs expert Miller directs the team towards a house suspected of being a drugs factory. Angelina Costeros, a former chemical factory employee, is brought in but refuses to incriminate likely co-defendant Jensen Raphael until Dinah and colleague Spike unite to get her to talk. Consequently Dinah and Joy go undercover to bust Raphael. The operation is successful and Viv praises the two ...

Following the death of Samina Hassan in an arson attack the team goes undercover at a wedding to arrest the groom Jimmy Webb, a known racist. CCTV had shown him arguing with Majib, Samina's widower, to whom he had lent a large sum of money, whilst Samina's father, a strict imam, has quarrelled with her over her feminist stance. In the event the previously reserved Joy proves herself by solving the case and flushing the killer out into the open. Spike interviews Patrick Llewellyn, an unassuming gay man who runs the support group attended by murder victim Lucy - who had...

As Dinah is driving to work she sees David Brazier kill himself by stepping in front of a car and when the police visit his house they find his wife dead in bed with a huge operation scar. Later they arrest a teenager following a disturbance. He also has a scar and a wad of notes and tells of a traffic in human organs for cash. Joy and Dinah track down another potential victim, leading to a successful arrest. Meanwhile Teresa Adamson is found dead after joining a website, whose organizer identifies a subscriber calling himself Handyman, whose interest is in Downs ...

Forensics officer Miller is engaging Handyman online posing as a young girl when the team is called out to a stabbing. The victim is Christy Feeney, now given a new identity as Noel, but who, aged ten, was convicted of murder. After hearing his confession pregnant wife Liz feels especially vulnerable but Viv suspects Christy's aggrieved uncle of offering a bounty to his nephew's killer. Christy does not help matters when he flees police protection to speak to Liz, though he does lead them to his attacker. Olivia, another Downs Syndrome girl, agrees to be bait to catch...

Cathy has information leading to a suspect in her abduction, but later tells Dinah there was also an accomplice. A badly beaten man is found outside a scrap yard and appears to be connected with a man police find locked in a shed.

A jogger is shot and killed, but Viv believes their young suspect acted on behalf of an adult with a grudge. Dinah begins her own secret investigation to determine if Viv is protecting the identity of the Handyman's accomplice.

Dinas clashes with Deering, setting off an irreversible chain of events, and an attempt to save the lives of a mother and baby goes disastrously wrong.