In 2008 body-builder Mark Rix died of a heart attack, seemingly caused by a surfeit of steroids. Now a sword is found in his old lock-up, which decapitated an unknown man just before Mark died. Mark was a member of Imperium, a group re-enacting life in Ancient Rome and Steve and Sasha learn from Imperium members Julia Kane and Tim and Tessa Dugdale that he believed himself to be Marcus Rex, incarnation of a gladiator. Forensic scientist Fiona Kennedy identifies the murder victim as a Romanian gangster who sold illegal steroids and the team deduces that Rix used Imperium's foreign dates to import them. After confessing to Fiona that his estranged wife Sarah is in a secure unit, having tried to kill him and his daughter, Danny goes undercover at Imperium, where he recognizes Julia as another undercover cop. Eventually the team learns the truth about both men's deaths from Julia before Danny goes on a date with Fiona.

Gerry is personally involved when the body of Martin Ackroyd, his first inspector when he joined CID, is discovered having been missing for thirty years. Prime suspects are former officers Bryant and McCabe, whom Ackroyd believed to be corrupt and are now involved with career criminal Dominic Chapman, as is Ackroyd's ex-superior Ronald Sainsbury who colludes with them to discredit Gerry. Gerry tracks down Tommy Naylor, another crook the dead man had in his sights and whom Bryant and McCabe unsuccessfully attempted to frame. Gerry decides to take the law into his own hands after his daughter Caitlin is threatened but this only makes him seem guilty of the murder in Sasha's eyes.

With evidence suggesting that his cosh was the murder weapon and a trumped-up assault claim from Sainsbury things look bleak for Gerry but DAC Strickland is sure of his innocence and lets him go. With dangerous men in pursuit Gerry goes on the run with Danny, to whom he relates that Ackroyd was as corrupt as any of the other suspects and was in Chapman's pay. They call on Tommy Naylor, who directs them towards honest Ted Case, another retired officer and he gives them evidence of Ackroyd's involvement with Chapman. This in turn leads Gerry back to Bryant and McCabe and arrests are made, followed by recrimination, chicanery, a funeral and a departure.

Ted Case joins the team to reopen the murder of vicar Leonard Whitechurch, a white man with a black wife who was stabbed in 2006 after receiving racist hate mail. His widow Alicia tells them that his curate Wendy had a crush on him but she hung herself two years after his death. The poison pen letters are traced to ex-convict and white supremacist Kevin Duncan but Ted believes the motive to be more complicated than purely racial. Duncan admits he wrote the letters in revenge as the victim disapproved of his dating his daughter Sally but a revelation from Leonard's younger son Luke exposes a rift in the family and leads to the solution of the murder.

When the recently deceased pathologist Dr Hatton's findings are discredited the team looks into the 2005 drowning in his bath of cricketer AJ Da Silva, a suicide according to Hatton though AJ's father and brother are convinced he was murdered. Ted learns from coach Keith Ainsworth and former captain Ryan Reed that AJ was thoroughly disliked by the other cricketers in his side as an arrogant, drunken womaniser. In fact his affair with a team mate's wife was held responsible for the man's suicide. After another person is found dead the key to AJ's demise is found to be match-fixing and its consequences and, the case solved, Ted springs a surprise on his colleagues.

In 2002 married Anna and Jim Briggs - who worked for a look-alike agency - were found dead in a supposed suicide pact. Now Anna's phone has been discovered, containing amorous texts to a mysterious lover. The team interviews other look alikes, including Anna's sister and professional rival, Lesley, and ex-soccer star Mikey Bishop, whom Jim impersonated and who says that he met Jim and found him harmless. They also find Mikey's wife Clara is over-protective of her husband as it becomes apparent that he was Anna's lover. a truly bizarre role reversal however proves the key to solving the murders of the two victims.

The 17 year old skeleton is unearthed of Cheryl Sheekey who disappeared after her pub quiz team syndicate won a fortune on the lottery. In the frame are the quiz team organizer Craig Bentham, his wife Lizzie, who suspected him of an affair with the dead woman, Cheryl's childhood friend Eleanor and her husband Terry, who squandered his winnings and is now on hard times, making him the prime suspect. The team must establish which, if any of them, killed Cheryl as well as trying to set Sasha up with a boyfriend.

A blood-stained bust uncovered in a graveyard links to the 2008 murder of alternative health practitioner Jason Henway. Angela Morris blamed him for taking her late mother Gwen off chemotherapy but had an alibi. Jason's business partner Evan Langley stood to gain but points the team towards Jason's brother Douglas, a doctor practising cryopreservation, keeping the clinically dead alive through low temperatures, since he left the business having quarrelled with his brother on his wife's death. As well as solving the murder the team must also deal with Sasha's departure when she is offered an appetizing promotion.

On New Year's Eve 1999 progressive mental health campaigner Greg Collins was murdered and now the discovery of his diary is found, chronicling his fear of his likely fate. The team interviews his colleagues including Toni Pembury, who tells them that Greg was battling a drugs company, and Samia Khan, now a peeress, who fell out with Greg after leaving his mental health charity to set up one of her own. Then they are ordered to halt the inquiry, supposedly in the wake of the mishandled Henway case. When Greg's journal goes missing they must work unofficially to solve his murder - and work fast since UCOS is threatened with being disbanded.

The 17 year old skeleton is unearthed of Cheryl Sheekey who disappeared after her pub quiz team syndicate won a fortune on the lottery. In the frame are the quiz team organizer Craig Bentham, his wife Lizzie, who suspected him of an affair with the dead woman, Cheryl's childhood friend Eleanor and her husband Terry, who squandered his winnings and is now on hard times, making him the prime suspect. The team must establish which, if any of them, killed Cheryl as well as trying to set Sasha up with a boyfriend.

Gerry is personally involved when the body of Martin Ackroyd, his first inspector when he joined CID, is discovered having been missing for thirty years. Prime suspects are former officers Bryant and McCabe, whom Ackroyd believed to be corrupt and are now involved with career criminal Dominic Chapman, as is Ackroyd's ex-superior Ronald Sainsbury who colludes with them to discredit Gerry. Gerry tracks down Tommy Naylor, another crook the dead man had in his sights and whom Bryant and McCabe unsuccessfully attempted to frame. Gerry decides to take the law into his own hands after his daughter Caitlin is threatened but this only makes him seem guilty of the murder in Sasha's eyes.

When the recently deceased pathologist Dr Hatton's findings are discredited the team looks into the 2005 drowning in his bath of cricketer AJ Da Silva, a suicide according to Hatton though AJ's father and brother are convinced he was murdered. Ted learns from coach Keith Ainsworth and former captain Ryan Reed that AJ was thoroughly disliked by the other cricketers in his side as an arrogant, drunken womaniser. In fact his affair with a team mate's wife was held responsible for the man's suicide. After another person is found dead the key to AJ's demise is found to be match-fixing and its consequences and, the case solved, Ted springs a surprise on his colleagues.

In 2002 married Anna and Jim Briggs - who worked for a look-alike agency - were found dead in a supposed suicide pact. Now Anna's phone has been discovered, containing amorous texts to a mysterious lover. The team interviews other look alikes, including Anna's sister and professional rival, Lesley, and ex-soccer star Mikey Bishop, whom Jim impersonated and who says that he met Jim and found him harmless. They also find Mikey's wife Clara is over-protective of her husband as it becomes apparent that he was Anna's lover. a truly bizarre role reversal however proves the key to solving the murders of the two victims.

A blood-stained bust uncovered in a graveyard links to the 2008 murder of alternative health practitioner Jason Henway. Angela Morris blamed him for taking her late mother Gwen off chemotherapy but had an alibi. Jason's business partner Evan Langley stood to gain but points the team towards Jason's brother Douglas, a doctor practising cryopreservation, keeping the clinically dead alive through low temperatures, since he left the business having quarrelled with his brother on his wife's death. As well as solving the murder the team must also deal with Sasha's departure when she is offered an appetizing promotion.

Ted Case joins the team to reopen the murder of vicar Leonard Whitechurch, a white man with a black wife who was stabbed in 2006 after receiving racist hate mail. His widow Alicia tells them that his curate Wendy had a crush on him but she hung herself two years after his death. The poison pen letters are traced to ex-convict and white supremacist Kevin Duncan but Ted believes the motive to be more complicated than purely racial. Duncan admits he wrote the letters in revenge as the victim disapproved of his dating his daughter Sally but a revelation from Leonard's younger son Luke exposes a rift in the family and leads to the solution of the murder.

With evidence suggesting that his cosh was the murder weapon and a trumped-up assault claim from Sainsbury things look bleak for Gerry but DAC Strickland is sure of his innocence and lets him go. With dangerous men in pursuit Gerry goes on the run with Danny, to whom he relates that Ackroyd was as corrupt as any of the other suspects and was in Chapman's pay. They call on Tommy Naylor, who directs them towards honest Ted Case, another retired officer and he gives them evidence of Ackroyd's involvement with Chapman. This in turn leads Gerry back to Bryant and McCabe and arrests are made, followed by recrimination, chicanery, a funeral and a departure.