A two-year-old girl is abducted from her home and her dysfunctional family comes under immediate suspicion, but then a convicted child killer is also connected to the case.
Jack and Charlie investigate an assault on the owner of the Green Pit nightclub in east London and discover the victim's sister unconscious in the cellar, with blood pouring from a head wound. The detectives' efforts to piece together what happened are hampered by the lack of CCTV footage, and the case takes a confusing turn when a 19-year-old student is found dead with a flyer for the club in his pocket.
Jack and Charlie's hunt for a serial rapist becomes complicated when the latest woman to be attacked turns out to be Diane Ackerman - the wife of the station's chief superintendent Howard. A routine background check reveals that the police had recently been called to their address and Diane has a bruise on her throat that predates the rape.
Euthanasia campaigner Terence Holland is found unconscious in his penthouse flat by his doctor after an apparent drugs overdose, leading to the assumption that the terminally ill man had found someone to help him die. However, evidence at the scene prompts Martha to speculate that this could be a case of attempted murder.
Jack and Charlie are called out in the early hours after a 13-year-old girl is stabbed. The hospital reports back that she was eight weeks pregnant, shows signs of possible self-harming and had been previously sexually assaulted, while a number on her mobile phone belongs to the cab driver who drove her to hospital and claimed he did not know her.
In the first of a two-part story, DI Martha Bellamy's neighbour, barrister Jonathan Moxton, is discovered at his home with serious head injuries, his wrists bound with a belt and a pair of knickers stuffed in his mouth. DS Jack Weston guesses he was involved in a sex game that went badly wrong and suspicion falls on Saul Hammond, the man who found him.
The body of a student, Michael Collins is found on Crowford common. The killer is suspected to be the person who attacked Moxton.
Jack leads an investigation into the dark world of child sex offenders. He becomes too emotionally involved within the case after a brutal attack is made on an amateur paedophile hunter Scott Freeman.
The suspected leader of the paedophile ring is murdered and the hunt is on to find the killer.
DI Martha Bellamy welcomes back DS Jack Weston after a period of enforced leave following the paedophile investigation, warning him this is his final chance. Jack and DC Charlie Steele investigate when a popular art teacher is found with life-threatening head injuries at a sixth-form college, with suspicions falling on handyman Ben Peel and head Rory O'Hanlon.
The detectives investigate when a young woman is fished out of the Thames in the middle of the night, badly burnt and barely alive, with the only witnesses at the scene being a few homeless people who saw a man with a white van dumping the body in the river. Charlie runs the victim's distinctive necklace through the database and links it to Sian Jenkins, who was registered as missing in 2012, and events take a further turn when DNA taken from under her fingernails is matched to a girl who disappeared when she was eight almost a decade previously.
Teenager Asif Khan is seriously injured after a petrol bomb is thrown into the family home. His father Jamal accuses shady businessman Gregor Forrester of intimidating him into a property deal and using disgraced former policeman David Eboda, a former mentor to Jack, as his heavy. When Forrester's son Zach goes missing it seems that Jamal is out for revenge though he has an alibi, which is more than Forrester has for the night of the arson attack. A secret love triangle and an attempt to give the illusion of a kidnapping are revealed before the case is closed.
After teenager Mandy Granger goes missing the body of a young girl is found dumped on waste ground though Mandy's mother Natalie claims it is not her daughter. The police discover that Mandy made the 999 call and CCTV reveals her violent father Andrew fighting with Jez, her boyfriend, who is a trans-sexual previously called Julie and Andrew is arrested. Then Oliver, who dated Jez when she was Julie, is in the frame, having sent her abusive texts. A drunken party which got out of hand eventually holds the key to who killed Jez and what happened to Mandy.
Ken Baxter stages a roof-top protest over his missing soldier son Pete whilst Pete's mistress Sophie is the victim of a hit and run incident. Pete's friend Eddie is a primer suspect as is Sophie's husband Ricky whilst Sophie's friend Caitlin also has something to hide. Ricky is arrested for the hit and run but when Ken is also killed Martha and her team must look elsewhere for the guilty party.
After an early release from prison due to cancer, Dean Price is beaten, stabbed and left for dead in a copycat crime, identical to the one he was convicted of having a part in eight years ago. The father of the original victim comes under suspicion, after reports of an argument between him and Dean and evidence of blood on Dean’s kitchen floor. In an effort to get to the bottom of what happened, the east London detectives decide to reopen the original investigation.
The team are shocked by the shooting in broad daylight of a popular clergyman outside the boxing club that he runs for disaffected youths. Martha suspects that the vicar’s hug-a-hoodie approach has backfired - but the investigation soon moves into far darker territory…
The detectives are met with a wall of silence when they try to find out who was responsible for the brutal attack of an elderly widow in her home on a notorious London estate. The victim claims her life savings of £10,000 were taken from her spare room, but the team doubts her veracity. The investigation points towards numerous suspects, including the victim’s son, a man with convictions for robbery and cannabis possession, and another with a history of violence.
The unit is stunned when DI Martha Bellamy is murdered in her own home. DCI Daniel Drummond leads the investigation, bringing in officers from Major Crimes to help - but someone knows more than they are letting on.
A new murder victim is linked to the Bellamy blackmail case forcing Jack to pressure his old flame into testifying against her boyfriend, who Jack thinks is responsible for the blackmail and Martha's murder.
When a girl is raped on her way home, Jack tries to conceal his connection to the key witness in the case, Lucy. The 16-year-old has been living with him since he discovered that she is probably his daughter, and Charlie reluctantly agrees to keep his secret. However, it soon becomes clear that both girls are lying about that evening, and when more evidence emerges, Charlie cannot stay silent for much longer.
Jack finds it impossible to sit at home on the sidelines when his daughter is abducted.
The body of Sarah Kramer, who went missing eight years earlier is found and Jack interviews her widowed father Joseph, who tells him that Martha had been investigating the disappearance. Retired officer Ed Goddard, no friend of Drummond, reports to Gary that Sarah was an informant and Drummond her handler and secret lover whilst Jack also lets Gary in on Drummond's confession regarding Stan's death. Drummond covers himself to the team, throwing suspicion on Mo as the object of Sarah's investigation and her killer, to which he admits but adds that Drummond buried her ...
Alisha obtains evidence to incriminate Drummond from his wife Chrissy and, after she is attacked and it is stolen, its recovery proves that Drummond's son Luke was the attacker. Realizing that the game could be up for him Drummond goes to see Joseph and asks him to keep a secret. The connection between Joseph, Mo Jones and Drummond will eventually solve the mystery as to who killed Sarah, and Martha and her husband and bring Drummond down.
