Leo is stopped for drink driving and finds himself having to do community service in a rough part of South London, answering to a tough-talking community worker named AJ who is not happy to be saddled with a 'drunk whitey'. Leo tries to keep his head down, do his hours and get out. But when one of the lads is stabbed near their playing fields, Leo steps in and saves the boy's life, winning him new respect from AJ and the kids. Nikki investigates the death of a young girl from the same area who, it seems, was murdered.

Frustration within the team builds as Harry and Nikki struggle to find any useful evidence from the post-mortems to help the police. No one will talk, and they have no leads. Leo worries for Levi, who is sucked further into a world of gangs and violence.

Harry acts as mentor to Holly Farr, a young and eager medical student, who charms him into involving her in his latest case - the post-mortem of a woman found dumped on the side of the road with her face skilfully removed. Nikki is called upon to reconstruct the victim's face, and the team cannot fathom why it would have been removed in such a careful manner until Holly discovers a connection with a dangerous Russian criminal.

Harry tangles with a Russian oligarch over the murder of a journalist.

The team investigates an armed raid on a suspected terrorist cell in which two terrorists and a police officer are killed. When Nikki's findings point to a bungled raid with innocent lives being lost, people start to pass the buck. Fighting hostility and closed ranks, she beguiles her way into the police armed response unit to try to uncover what might have gone wrong. Harry is given the task of identifying one of the victims.

Nikki visits Isra, the teenage sister of one of the suspects, and the only key eye witness. She insists that her brother was innocent, but after Nikki discovers how harshly Isra is being treated, the team starts to suspect a cover up. Rhys continues to run, and there's a shock in store for Harry when he realises he knows the identity of the unknown victim.

When the badly decomposed body of a Hasidic man is discovered on disused wasteland, Harry is tasked to investigate his death, and to treat the community with care. Everything points towards a brutal anti Semitic murder by a polish labourer - but when the time of death contradicts his wife's last sighting, Harry becomes suspicious. Meanwhile, Leo investigates the death of a female Australian backpacker at a house party. The partygoers are saying it is a straightforward drug death, but markings on her body suggest a sexually motivated crime. Leo finds himself being given short shrift by her friends as he tries to piece together the moments leading to her death.

The death of a second Hasidic boy, Chaim, convinces Harry they are looking for a Jewish killer, but without concrete evidence the police are reluctant to upset an already fragile relationship with the community. When a Hasidic boy, Binyomin, appears to take the law into his own hands, attacking a Polish builder, Toni, Harry makes a shocking discovery that threatens to strain relations even further.

When the half-naked body of a 12-year-old is discovered floating in a drainage ditch near his school, the team is called in, bringing Nikki back in contact with one of her former teachers, Noel Hopkins, now headmaster. During Harry's preliminary examination they find clear signs of abuse, and when the police discover the victim was last seen with another boy, Liam, who has also gone missing, they fear he may have been abducted. Liam is still out there, the hope is that he is still alive, and the team, under increasing pressure from the police, must find clues from the dead boy's body in order to save the living.

Nikki's loyalty towards her former mentor, Noel Hopkins, is severely tested when past allegations of sexual misconduct from a former student surface. Leo and Harry refuse to give up their search for Liam, as they try to identify and locate a toxic chemical which was found in both bodies. If they can find the source of the chemical, they may find where Liam is being held.

When Rachel Harrington's bones are found in Zambia, her expat father and local mining engineer, Stephen, asks the team to come out to investigate. His boss, Peter, is a childhood friend of Nikki's. Rachel had been accusing the government of a health cover-up, and an initial examination shows evidence of multiple stab wounds. But as the team investigates further, it seems the government weren't the only ones to have been rubbed up the wrong way by Rachel.

Nikki clashes with Zambian police as she investigates the death of a British medical student.