The members of a prestigious golf club come under suspicion when the UCOS team investigate a child murder.

Deputy Assistant Commissioner Robert Strickland is the new boss in charge of the Unsolved Crime and Open Case Squad (UCOS). He asks the team to look into the death of David Barrie, a top barrister found in his car in 1980 after being bound and gagged.

Luck turns against Standing when he loses a poker game, owing bookie Michael Jacobs £10,000. But Michael offers him a chance to clear his debt by finding out what happened to his dad Joe, who died after being mugged outside Walthamstow stadium in 1983.

As the series comes to an end, the desiccated, neatly carved-up body of a butcher who disappeared more than 30 years ago is discovered, leading Sandra Pullman and her boys to pay a visit to Smithfield meat market in London, the original murder scene. It's a pity the butcher is dead, because he has a few questions to answer about why the body of a doctor was found hanging from a meat hook all those years ago at the back of his market stall. It's an episode peppered with revelations. We discover Gerry Standing's very interesting family history - he's descended from French Huguenots and is thus tormented by his colleagues for being a fake cockney, much to his annoyance: "Je suis ang-bleedingglais!" he protests. But it's Sandra who has to face up to a startling personal disclosure that has a direct bearing on the case and also throws a whole new light on her father. For once Gerry, Brian and Jack are left completely speechless.

A recent rape is linked to two similar attacks at a chocolate factory 10 years previously, leaving the team no choice but to reopen all three cases. The detectives uncover news of an unhappy workforce, learning of an alleged suicide, and their investigation becomes even more complicated when they discover a severed finger was found in one of the company's snacks. After a visit to the doctor, Gerry decides to quit smoking, and instead of resorting to nicotine patches or gum, he enlists Sandra to help him quit

When the gun used to murder a talented young boxer 11 years ago surfaces in an armed robbery, UCOS are drawn into the darker side of professional boxing in a case that causes conflict and friction among the team.

Sandra's old flame DCI Larson, head of the Met's arts and antiques squad, asks the team to reinvestigate the murder of antiques dealer Mal Baxter. His death was originally thought to be the result of a burglary gone wrong, but new evidence suggests Baxter was a police informant while conducting underhanded deals.

The team reopen the case of zookeeper Zac Halsey, originally thought to have been mauled to death by a tiger, when blood evidence discovered in his lodgings suggests he was killed before he was found in the tiger's enclosure.

A young woman's paternity test leads to the reopening of a notorious murder case from the seedy underworld of 1980s Soho in which the prime suspect was mysterious ex-jazz chanteuse Angela Gold. Meanwhile in UCOS, feathers are ruffled when recently retired police officer Dan Griffin joins the team.

The team investigate the death of a personal trainer who had belonged to a Roman reenactment society and discover a gang selling illegal steroids, but the motive for murder may not be all it seems.

And Danny Griffin starts to become attracted to his forensic pathologist colleague Fiona Kennedy just as he receives some troubling news about his wife.