After a fatal stabbing in a crowded market place, the pressure is on to make Londoners feel safe again. Ronnie and Joe have a new boss to contend with, DI Elisabeth Flynn is determined to put her stamp on the MIU, declaring her own personal crackdown on knife crime. Under pressure from all sides, Ronnie and Joe struggle to gather enough evidence to charge the youth they believe to be responsible. However, when the suspect inadvertently confesses to Ronnie, he thinks he's got him – but with the confession uncorroborated by anyone else, Ronnie begins to realise that his honesty is in question.

When a series of shootings claims one of their own, Ronnie and Joe have little time to grieve – they must catch the killer before he or she can reach the next people on the hit list.

A bloody hotel room and a stolen credit card lead Ronnie and Joe to Charles Hutton, a member of the wealthy upper-class who dotes on his wife Camille, and daughter, Georgia. Without a body it's difficult to ascertain the crime, but before long, Ronnie and Joe have enough evidence to suggest that Georgia gave birth in the hotel room – but where is the baby? Georgia and her boyfriend are difficult enough for the CPS to prosecute but to make matters worse the defence counsel turns out to be an old nemesis of Jake's, Maitland Cosby. But as the evidence against the young couple stacks up, how far will Georgia's father go to protect her future?

When Ronnie and Joe are called to a suicide it doesn't take long for Ronnie to suspect foul play: Ranya Habib had no reason to kill herself. Although they are initially suspicious of a Dr. Elsayed who recently arrived in the country to visit Ranya. Although they can't find any evidence against him, Dr. Elsayed's medical history includes the practice of FGM, female genital mutilation, on young girls. Appalled by this, Kate struggles to remain professional and jeopardises her entire career leaving Jake to prosecute the case alone.

The death of a seemingly innocent family man leads Ronnie and Joe to go on the hunt for the murderer, but they soon discover that the accused is Eddie Stewart, just so happens to be former DI Natalie Chandler's father. No one can understand why Eddie would commit murder, least of all Natalie who argues with a sympathetic Jake when she confronts him over the charge against her father. Natalie wastes no time in getting Ronnie to go above and beyond to help her find the real killer, even if that means getting him into trouble with a frustrated DI Leyton.

Whilst helping out the drugs squad on a bust, Ronnie and Joe stumble upon a body that has been hidden inside the boot of a car in the Thames. It turns out that the man was Taylor Kane, a black undercover policeman who went missing in the 1980s during the Brixton riots. DI Leyton finds himself personally putting his head above the parapet when he gets an unexpected visit from the Commissioner. Accusations of are thrown around as our heroes get in deeper and deeper when the case hits the headlines, it's time to pick a side as loyalties are tested and careers are put on the line for justice.

The stabbing of a psychiatrist who treated teenagers and children initially leads Ronnie and Joe to question his violent adolescent clients. However, when they uncover evidence that points to him having an affair with one of his patients, they begin to suspect that his wife, Alison, might have had more motive than anyone else. Although she initially denies killing her husband, Alison quickly changes her defence when the evidence stacks up against her. Her argument that she wasn't in her right mind and lost control when she stabbed him, challenges the prosecution, and Kate questions whether they should be trying her for murder at all.

Ronnie and his new partner DS Joe Hawkins are leading an investigation into the death of jeweller Harry Bernstein, who is found dead with no hands or teeth. His wife Lindsey, her lover David, and a former business associate are all possible suspects. But the case takes a surprising turn when Bernstein's sister turns up with his severed hands. They were delivered to her house in a box to lend weight to a very simple message: ‘not guilty'.