Watch Law & Order: UK Season 4 in Australia

The police investigate the murder of a former professional footballer, Robert Nichols, who is found lying beside his car bludgeoned to death. He was on his way to meet his sister and was apparently replacing a flat tire when the attack occurred. The only thing taken was his very expensive watch. They manage to trace a passerby, Mike Jones, who initially denies having seen anything but eventually admits he was helping Nichols fix his flat. The police are naturally suspicious and believe Jones may have been the perpetrator. In checking into Nichols's background however, they learn he was a big-time gambler and owed well-known mobster Don Marsh a quarter of a million pounds. Jones obviously has good reason to lie since he saw who killed Nichols but the mobster has made it clear that his life is in danger if he testifies.

A judge is badly injured when she is shot during what appears to be a car robbery. The investigation reveals that a hitman had been hired to kill her.

The case starts with the murder of a doctor in the car park of the hospital where she works. What initially seems like a crime of passion soon unravels into a conspiracy involving senior government officials. Risking their careers, James and Alesha must get to the bottom of this case before another life is destroyed.

The police investigate a suspicious fire that resulted in the death of 13 year-old Ian Parnell. His mother Megan managed to escape but the pathologist confirms that Ian died of smoke inhalation. The boy was severely disabled and unable to care for himself. They follow several false leads including an absent father who is behind on his support payments and a couple of neighborhood lads who were known to have harassed the dead boy. In the end, the evidence points to the mother. In court James and Alesha come up against a barrister who refuses all reasonable offers to settle the case. His disdain for his client leads him to mount a series of increasingly ridiculous defenses. When the truth finally emerges, the Crown prosecutors face a moral dilemma.

DS Devlin and DS Brooks investigate the murder of a 13 year-old boy boy, Sean Monroe, the son of a fellow police officer who was killed and put down a storm drain. A note found on the body points to the work of Andrew Dillon, who was sentenced for an earlier racial murder and is serving his sentence. The racial motivation for the killing seems confirmed when a second boy, Dev Desai, is found strangled with the same note in his pocket. However, their investigation leads to a security guard, Marcus Wright, who admits to having encounters with both boys at the shops where he works. He says the boys deaths were God's will and he was simply doing God's work. If Wright is to be believed, it means that Dillon was wrongfully convicted. The case becomes personal when James Steel is accused of having purposely buried a witness statement that would have likely exonerated Dillon. He finds himself in dock but the judge allows him to conduct his own defense.