This police drama follows the activities in and around Sun Hill, a police station located in the fictional East London borough of Canley. The focus is not just the gritty reality of police work, however; the lives and loves of the officers who staff the precinct get equal play.
When a young mother is found badly beaten in an alleyway, Sun Hill CID is drawn into her tale of debt, blackmail and a complex love life.
A couple return from a night away to find their baby has been abducted from her bed, and the story offered by the child's nanny turns out to be unreliable.
The baby's body is found and the evidence stacks up against the nanny's boyfriend, but Sam and Jacob's gentle interrogation produces another startling suspect.
When a talented young athlete is found battered to death, officers interrogate guests at a house party he had attended earlier that evening.
Heaton plays a psychological game, putting pressure on the teenage partygoers by holding a press conference to uncover the truth about the death of their friend.
Human remains found in a park turn out to be those of a student who went missing 20 years previously, and the case brings Heaton face-to-face with an old adversary.
The discovery of two more bodies convinces Heaton his suspect is a serial killer, but the man he sent to prison 20 years ago sticks to his story that he is innocent.
Heaton's suspect provides an alibi for one of the murders, and helps the police by identifying everyone involved in staging the rave events attended by the victims.
When a cab driver is badly beaten and robbed, an electronic travel card found near the crime scene provides a lead to a volunteer working on the Jasmine Allen estate.
Nate falls for a paramedic called to attend to the victim of a fight, but is later forced to arrest her brother for his part in the incident.
A stabbing victim proves uncooperative and clearly has something to hide. Nate is furious to learn his new love interest agreed not to report the crime.
Max's Polish ancestry proves useful when he investigates corruption in Sun Hill's immigrant community.
Max sets out to find the teenage murder suspect who has gone on the run after being tipped off by his stepmother.
The driver of a lorry hijacked by masked raiders in an isolated lay-by admits to smuggling a woman and her child into the country to escape a violent marriage.
Stolen goods are returned to the house they were taken from - apparently by a remorseful burglar - but as the case takes a twist, Leon's integrity is called into question.
A recovering heroin addict is thrown out by her boyfriend when he discovers drugs in their flat, only to learn her five-year-old daughter has gone missing.
Callum arrives at a crime scene expecting to arrest a woman accused of theft, but the suspect turns out to be a victim of domestic abuse who desperately needs help.
A reluctant Nate is appointed as Safer Schools Officer at Deansgate Comprehensive following an arson attack, and Smithy is stabbed during the investigation.
When a pupil collapses in the corridor, Safer Schools Officer Nate uncovers a drug problem involving a local dealer, and a youngster is taken into care.
Safer Schools Officer Nate is horrified to discover the extent of peer pressure, drinking, underage sex and bullying among the pupils of Deansgate Comprehensive.
A hate campaign sparked by an earlier rape case divides pupils and parents at Deansgate Comprehensive, leading to schoolyard confrontations and classroom fights.
A school governor takes his daughter out of Deansgate Comprehensive after she admits to breaking into a classroom at night. Nate finds teacher Becky James beaten up.
As Becky James recovers in hospital, Nate learns she once had a relationship with school governor Russell Patterson, and it was he who arranged to have her laptop stolen.
Newly promoted Sergeant Diane Noble returns to Sun Hill and finds herself breaking up a rooftop party on a building site, where a youngster on drugs has a serious fall.
A drugs runner wearing a hoodie evades arrest, but crashes his stolen car, seriously injuring his passenger and leaving CID with three suspects.
A man suffering from motor neurone disease is badly beaten in his home, and CSE Eddie Olosunje jumps to a hasty conclusion that an aggravated burglary has taken place.
The resident magician of a social club turns to crime to fund a gambling habit, and falls prey to a blackmailer threatening to harm his girlfriend.
When Nate pulls a suicidal woman from the Thames, Terry discovers she is carrying a bag of heroin. Beth tells Tony she has applied for a transfer.
Max is convinced a woman shopper caught on CCTV is being used as a decoy when a toy shop is robbed and the manager is left with a serious gunshot wound.
Beth plans to kiss Nate at her leaving party and finds herself working with him on a domestic incident involving a boxing club owner.
The Sun Hill watch realise Millie must have been captured along with the missing woman, and a guilty Max resolves to bring her back alive.
A have-a-go hero is hurt during a raid on a jewellers, but promptly disappears from the hospital. Investigations reveal he is wanted for murder.
Stevie and Max face an investigation following the near-fatal accident of a suspect they were pursuing, and professional differences come between them.
When a teenage girl goes missing in the West End, Mel discovers she was upset by her father's death and moving to London from Manchester with her mother's new partner.
In Sam's last case at Sun Hill, she organises a drugs raid based on reports from an old informant, but the dealers get wind of the operation.
Inquiries reveal that the girl was kidnapped because the dealers wanted their money from her father - and Sam's last case ends in success.
Jack's estranged son Ben is released from prison and Mickey is shocked to learn he is selling drugs for a notorious dealer who is still inside.
Despite Jack's reservations, witnesses reveal his son kept faith with the police and did not fire the fatal shot when the drug deal was ambushed.
Smithy and Callum break up a street fight and encounter bar owner Jason Devlin, who reveals a vicious streak.
Following the fire at the E1 bar, investigations reveal that cocaine and forged identity documents were kept in the barman's flat above the premises.
Smithy proves to be a hero when a driver abandons his lorry full of illegal immigrants in the road and a girl is found trapped under boxes in the trailer.
The bag in Jason Devlin's car proves to contain jewellery stolen from his Afghan tenants, but Smithy is accused of planting the evidence.
Tensions mount between Callum and Smithy as the Sun Hill officers undergo extra riot control training, and the two sergeants come to blows.
Devlin puts pressure on the prosecution's star witness and Smithy is forced to face a barrage of questions about his behaviour during the Westgate riot.
A youth suspected of assaulting three youngsters is run over and killed while being pursued by Callum and Ben. The grieving mother supplies an alibi for her son.
The assault case becomes murder when one of the victims dies and Banksy finds himself in conflict with his colleagues when he tries to defend the youngsters.
Mickey helps a teenager who claims she has been raped. Initial suspicion falls on her current boyfriend, but sensitive questioning reveals the incident took place two years ago.
Stevie questions a man arrested for attacking a fellow drinker in a pub, and becomes emotionally involved when she learns the suspect is depressed after losing his job.
A child abandoned in a busy market alerts police to the fact his nanny has been abducted and left badly beaten on a construction site.
Neil investigates the possibility somebody is seeking revenge on a psychiatrist whose partner has been injured in a hit-and-run incident.
When a newsagent is beaten to death, the telephone used to tip off the police turns out to belong to Joseph Sissoulu, whose son Danny was recently murdered.
Neil and Max investigate when a 17-year-old girl who recently left foster care is shot dead, and the prime suspect turns out to be her mother's partner.
A known paedophile and his friend are suspected of creating indecent images of a child, but Banksy has difficulty telling which of the pair is covering for the other.
Jo persuades a former prostitute to help her catch a big-time drug dealer, but the ensuing raid draws a blank.
Max's key witness in the drugs case is attacked and left with serious head injuries, and her 12-year-old son goes missing.
A distressed 17-year-old is found traumatised after years of prolonged abuse, and Stevie struggles to establish his identity after the boy's sister fails to recognise him.
When an eight-year-old is abducted from outside his school, Terry is appointed Family Liaison Officer and finds himself keeping the peace between the child's divorcing parents.
Leon asks a prison officer friend to smuggle a bugged telephone into Longmarsh jail, where a drug dealer is planning a murder.
A frantic mother reports her car has been stolen with her baby inside. The frightened child is eventually found covered in bruises, indicating she has been abused.
A shopkeeper takes matters into her own hands to tackle the menace of drug dealers terrorising the Manley Road estate. Tony Stamp shocks Smithy with unexpected news.
Tony Stamp spends his last shift at Sun Hill comforting a mother whose 18-month-old child has sustained serious head injuries under suspicious circumstances.
Grace is summoned to a Soho brothel, where a woman is holding a man at knifepoint, demanding to know the whereabouts of her missing sister.
A convicted murderer learns his daughter has gone missing, and the Sun Hill detectives discover she was going out with the victim's son.
Mickey goes undercover as a homeless man after a body is found in the river wearing a tramp's coat over designer clothes. Millie says goodbye to Sun Hill.
After another night on the streets, Mickey learns a second down-and-out has been murdered. Property developer Greg Simm falls under suspicion.