In the first series the team investigate who was responsible for a fake painting in the Queen's private collection; re-examine the unsolved case of a peace protestor found dead near a nuclear base in 1984; and respond to a dying man's request to clear his dead son of the murder of a ten-year-old boy.
Returning in 2005 for a second series, the police drama sees the squad being ordered to look into the unsolved murder of a barrister found bound and gagged in his car 25 years previously. The team also looks into an assault case that left the victim in a coma; reopens a 1992 abduction case when the woman who disappeared turns up alive and well; and investigate a claim that a celebrity chef murdered her husband during the 1960s.
In the third series Pullman reopens the unsolved case of a teacher murdered five years earlier. The squad reinvestigate the death of a union leader; try to find out why a spate of dog killings matches a series of animal slayings from 30 years ago; and Brian goes undercover to apprehend a criminal who is only allowed in the country for a week.
Returning for a fourth run in 2007, Pullman takes drastic measures to stop Jack exacting revenge on the hit-and-run driver who killed his wife. Pullman's mother needs to go in a care home and her first choice had a suspicious death a year earlier, leading Jack, Gerry and Brian to go undercover at the home; the squad reopen a murder case from 17 years previously; and the team look into the death of an elderly woman whose decision to leave her estate to her cats sparked a family feud.
A fresh batch of episodes for series five sees Jack's mind not on the job as a man faces trial for trying to murder him. The publication of a biography leads to the reopening of an old case; the squad investigates an arson attack that killed a radio DJ; and a deathbed confession leads the team to investigate the suicide of a 1970s rock star.
Returning in 2009 for series six, the drama follows Brian as he enters an addiction centre run by monks to treat his alcoholism. Jack examines a conspiracy theory that the American government was involved in the death of a journalist; the squad help a man who believes his wife is still alive; and the team re-examine the disappearance of an actress.
In series seven the team reinvestigates the death of a wealthy financier when a psychic informs his daughter she needs to resolve her father's unfinished business. Brian looks into the death of a professor who died after falling off the roof of his college; the squad are suspicious of a notorious paedophile's motive after he admits to the abduction and murder of a child 25 years previously; and a rape has the hallmarks of two similar attacks at a chocolate factory ten years earlier.
Returning in 2011, it begins with the squad reopening the case of a murdered palaeontologist. In later editions, the team reopens the 15-year-old case of a vagrant who was strangled on a train; DNA testing helps identify a body found in 1996; and new information links the death of a market trader to a series of drug rapes in east London.
In the opening edition, Jack announces he is quitting the team. In later shows, the remaining squad members reopen the case of a missing teacher when the remains of a body are discovered near the school where he taught; Pullman inquiries into the apparent suicide of a Foreign Office diplomat; and the team's feathers are ruffled by the arrival of retired detective DI Steve McAllister from Glasgow, brought in to help reinvestigate one of his original cases.
A new set of episodes premiered on BBC One in August 2013. In the series opener, Brian is suspended for punching a senior officer, while the rest of the team visit Gibraltar to try to uncover the truth about a 1982 murder. In later shows, the team reopens the 16-year-old case of an infamous getaway driver convicted of murdering his wife; Brian agrees to help Esther's friend find her missing brother; and the unsolved murder of a pornographer is reopened when his daughter provides DNA proof he was not her father.
As the series unfolds, an old friend asks Gerry to investigate the murder of his grandson, Danny's daughter leaves home for university, and Sasha agrees to go for dinner with her ex-husband.
In Season 12, Gerry has to face up to some skeletons in his closet, the team investigates the case of a murdered vicar and Ted leads a probe into the apparent suicide of a city trader.