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.

The London detectives investigate a brutal attack on a popular art teacher at her college.

The team investigates the case of a badly burned young woman who has been dumped in the Thames.

In the team's investigation of a petrol-bomb attack, Jack sets his sights on a reprobate property developer who has so far managed to elude conviction.

After a teenaged girl is found naked and severely wounded, Charlie tries to identify the victim and connect her to the case of a recent girl gone missing.

The team investigate a missing persons case when a soldier suffering from PTSD fails to turn up to his mother's funeral.

The team reopen an old case of a fatal stabbing, after a criminal involved in the original attack is left for dead in a copycat crime.

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…

When an elderly widow is brutally attacked in her own home on a notorious London estate, the team set out to find her attacker.

New colleagues join the team when DI Bellamy is shot dead.

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.