Pullman seizes the chance to solve a murder that she believes is linked to her first ever case, and the team start putting together a jigsaw puzzle of suspects from a photograph taken in a London park in the 90s. Eventually faced with increasing pressure to hand over the investigation, Sandra makes a huge decision, which is going to change UCOS forever.

Gerry attempts to clear his name before his enemies catch up with him. Sasha and Steve get Fiona's help to examine the evidence against the clock. Danny takes Gerry on the run as they look for the proof they need to prove his innocence.

Retired DI Steve McAndrew from Glasgow joins the team to reopen one of his old cases when the DNA of a woman who went missing as a teen turns up at the scene of a petrol station robbery.

The team unlock over three decades of secrets and lies on the Rock of Gibraltar and find the link which solves the murder of a playboy shipping heir from '98 and a young local boy from '82. With both cases solved, they return to England where Lane faces a disciplinary hearing, dragging up a death in custody from his past which threatens his career in UCOS.

The team investigate when a skeleton is uncovered in the foundations of a swimming pool.

Gerry feels spooked following the discovery of UCOS's latest victim, a policeman, whose body has lain untouched under a basement for the last 30 years. Accusations of police corruption and underhand dealings start to surface causing Gerry to face up to some skeletons in his own closet.

With Sasha back on fighting form, UCOS investigate the death of a cricket prodigy.

The future of the team is threatened and without having that to deal with, Sandra has to take drastic measures to prevent Jack from exacting revenge against the man who killed his wife Mary. Sandra also has the added benefit of trying to keep Jack’s actions from shady new recruit DCI Karen Hardwick while working on a 10-year-old murder case.

The team reinvestigate the disappearance of two young political activists.

The team reinvestigate a 30-year-old safety deposit robbery, and they soon find themselves being drawn into a case involving police corruption that threatens the future of the UCOS itself.

Sandra's private and professional worlds become intertwined when her mother has a fall and goes into a care home - but the establishment is revealed to be a scene of a suspicious death a year earlier.

Brian Lane enters rehab to treat his alcoholism, but the rest of the team soon join him.

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.

The team reinvestigates the 1950s murder of a young wages clerk at Battersea Power Station. Richard Dunne was hanged for Frederick Tully's murder, but his granddaughter, Hannah, is waging a campaign to have Dunne posthumously pardoned. The discovery of a suitcase containing used fivers in the attic of the Tully home sheds new light on the case, revealing a possible blackmail plot. A trace on the used fivers reveals that they should have been destroyed in the Battersea Power Station furnaces back in the 1950s, but were actually being saved by Douglas Murray, a friend of Tully's. It also becomes clear that the Battersea furnaces were being used to destroy other sensitive documents as well as used bank notes. When the team discovers a classified document relating to a massacre of civilians carried out by the British Army in Kenya, they uncover a blackmail plot spanning more than 50 years.

When Brian's dog finds a body, it prompts two people to confess to murder. It turns out that the body is over 600 years old, so Sandra, Jack, Brian and Gerry must discover why the pair took responsibility for a crime they couldn't possibly have committed and if they are the perpetrators of other killings. Elsewhere, Strickland is rather keen for them to solve an even more tricky mystery that is closer to home.

The UCOS team investigate the murder of a young peace protestor, killed at the outskirts of a nuclear base in 1984, and realise that they may be in danger of exposing a Special Branch cover up.

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

When a missing person case which Lane originally investigated gets re-activated, he's determined to crack it. But when the team swiftly uncover another two mysterious disappearances, they start to think they've got a serial killer on their hands.

In an attempt to make contact with his late wife Mary, Jack goes to see a clairvoyant. Instead he meets a girl who died in a shipping container in 1982 and has the case re-opened.

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.

In 1996 a beautiful newlywed, was attacked and left for dead. The only thing taken was her wedding ring and she has been in a coma ever since. The man jailed for the crime is now a born-again Christian and is protesting his innocence

The team re-examine the case of Hannah Taylor who was kidnapped from her home in 1992. A body, previously thought to be Hannah's, has just been identified as that of another kidnap victim

Tabloid editor Chris McConnell asks Sandra Pullman to help him prove celebrity chef Kitty Campbell killed her drunken husband Bertie 40 years ago at the height of their 60s TV fame.

Attractive widow and probate assessor Elise Allen asks Halford to find the rightful owner of a large, uncut red diamond, worth £15 million. She found the rare jewel in a flat rented by John Newman who died in 1982.

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.