After an attempt to rescue a kidnap victim the officer in charge, Supt. Sandra Pullman, who also shot a dog during the raid, is reassigned. DAC Donald Bevan puts her in charge of UCOS, a new unit focusing on unsolved cases. There are no resources available, but Sandra is authorized to hire retired detectives and turns first to her old boss and mentor, Jack Halford, who quickly signs on. Together, they interview a number of ex-policemen and settle on Brian Lane, a reformed alcoholic who retired after a prisoner in his custody died, and Gerry Standing, who seems to know as many criminals as policemen and who won't hesitate to cut corners if it will get him a result. Their first case is that of Roddy Wringer, who is released after 21 years in prison when one of the officers on his case is found to have been corrupt. Bevan is convinced Wringer is guilty and makes it clear that he expects Sandra to prove that. As the investigation progresses, however, it appears that Wringer may not have committed the murder that put him in jail and that the investigating officer knew that but withheld evidence.

The team investigate the murder of a policewoman 17 years ago, but what is Sandra's connection, and what secrets from her days at Hendon are revealed?

Sir Tim is Surveyor of the Queen's Pictures. He discovers that some of the pictures in his charge are fakes. But they never used to be. Was his predecessor making money on the side?

The team investigate the murder of a young peace protester, killed near a nuclear base in 1984. Was it a cover-up?

A 10-year-old boy is killed on a golf course. Some 20 years later, the team investigate but face obstruction from a snobbish golf club committee, who struggle to keep women out of the bar and to protect the memory of a Falklands war hero.

The team investigate the disappearance of an attractive young mum and her six-month old son in the 1970s. They also have to submit to a physical and psychological assessment.

Jack Halford hopes a clairvoyant will put him in touch with his late wife. Instead he is contacted by a girl who disappeared twenty years earlier.

New boss Robert Strickland asks the team to reopen the case of David Barrie, a barrister found dead, bound and gagged, in his car in the 1980s. The case was a rare instance of officer-in-charge Ronnie Ross's not getting his man. Chief suspect Michael, now a transsexual called Michaela, had an alibi, but Michaela is involved with Elaine Wanless, a former brothel-keeper who reveals the dead man's penchant for bondage. The team is convinced that both know more about the death than they claim.

UCOS reopens the case of a woman who has been left comatose for eight years.

In 1992, 18-year-old Hannah Taylor was kidnapped, and now a body, once believed to be hers, is proven to be another girl's. Hannah's mother, Madeline, an ex-alcoholic G.P., is prickly but admits to paying a twenty-thousand-pound ransom delivered by an-ex cop who was, in fact, her married lover. Jack suspects that this was a scam to part Madeline's former husband from twenty thousand pounds. The mystery intensifies when Jack traces Hannah, now married, who states that she left her mother a note to say she was going to a pop festival where she met her husband. It intensifies even further on the discovery that Madeline already knew Hannah's husband.

Sandra is approached by a tabloid editor who believes that former TV cookery queen Kitty Campbell poisoned her husband Bertie. Kitty obviously denies this but the Campbells' former assistant reveals that Bertie was a closet gay, much to Kitty's disgust. Esther Lane is bedridden after accidentally cutting herself while washing dishes and Brian realizes the extent to which he depends on her, the more so as, whilst watching archive film of the Campbells, she discovers the key to the mystery.

A friend of Jack Halford has a diamond that would appear to have been stolen.

The team is supposed to be investigating the conviction of Stanley Ackerman, whose wife is continually protesting in front of the station. The man was convicted of setting his factory on fire, but Jack sees a number of anomalies in the evidence. But having lost £10,000 in a poker game, Gerry is given the possibility of wiping out the debt when the winner asks him to investigate his father's murder 20 years earlier. The man, Joe Jacobs, had been attacked on the street, but it was put down to a mugging, with no arrests made. Gerry tries to investigate the case on his own, but his colleagues, including Supt. Sandra Pullman, are soon on to him. Jacobs was in debt to bookie George Morton, but they determine that his death was related to the kidnapping of a champion greyhound racing dog.

The UCOS team investigate the kidnapping of two 10-year-old boys over twenty years ago. Brian thinks it may be related to a current spate of kidnappings. What they know is that two boys, Daryl and Alan, were taken while fishing at an old pit. A few days later, they managed to escape unharmed, but the police never made an arrest in the case. One of the survivors agrees to undergo hypnosis, which reveals some additional clues. They soon learn that others fishing at the pit were either threatened or attacked over the years, including a champion fisherman who had held the record for catching the largest carp. As Brian spends more and more time by himself fishing at the pit, his wife, Esther, seeks Sandra Pullman's advice.

The team investigates the murder of an unidentified young woman who was found in the woods some 18 years previously. The original pathologist on the case, Professor Mears, has kept all of the evidence in the case and has longed for it to be reopened. He has even given the girl a name, "Millicent". Working with what little information they have (the young woman had red hair and had syphilis), they first seek to identify the girl. She also had been cut up by an expert carver. Throughout this time, Gerry Standing is going a bit mad, as he has given up gambling, but every horse he would have bet on has won.

DS Pullman decides to reopen one of her old cases involving the death of Nancy Murray in a car crash. Pullman is convinced that Nancy's husband, Stephen, introduced a mechanical fault and was out to get his wife because of an alleged affair she was having. Jack thinks the threats must have come from another woman, while Gerry thinks that she died for a simple reason: she was a woman driver. The team learns that Nancy was seeing a male prostitute twice weekly, and blackmail becomes a real possibility. The solution to the murder, however, is to be found by examining basic human needs and emotions.

With the recent release of Cabinet papers under the 30-year rule, Jack pushes to reopen the investigation into the death of Joe Walsh, a left-wing union leader. His body was fished out of the Thames in the mid 1970s and his death put down to suicide, but it was clear that the Cabinet wanted his antics stopped, and Jack wonders if someone might have taken those wishes a little too seriously. There were rumors that Walsh had fiddled the union books, and several of his contemporaries are convinced he was disposed of by MI5. Meanwhile, Brian decides to stop taking his medication, with expected results.

The team revive a 30-year-old investigation into animal cruelty when a dog is found butchered on Hampstead Heath. The original investigation focused on John Fletcher, who was the press officer for The Human Liberation Front, an organization that was set up to counter the animal rights movement but no longer in existence. They seek advice from James Farlow, the animal control officer at the time, but have few leads. They determine that the killer may actually have wanted to harvest the animal's vital organs. Meanwhile, Jack is feeling ill and is hospitalised with some unknown ailment.

The vicious criminal Chopper Hadley, who has been back in the country for a week, is searched for by the team. However, Halford is viciously intimidated and the squad start to realise the full danger of their target. Desperate measures are used and Brian is sent undercover to get Hadley once and for all.

A young woman insists that the suspicious death of a local librarian was because of witchcraft, and the team are drawn into the world of magic and the supernatural. A series of strange events occur, and they are put under increasing pressure. The squad become convinced that the supernatural exists and struggle to remain cynical.

When one of Gerry's informants returns to England and provides him with new evidence, the team re-open the case of a 1987 bank robbery where one of the bank employees was killed. The prime suspect was always Ray Cook, but the police could never get the evidence to charge him. Cook's alibi has always been that he was with his dying mother at the time of the robbery but the team find evidence that brings their basic premise into question. They also determine that the bank robbers may have had inside help, including that of certain police officers.

The team are on the case of the ice cream bandit, an armed robber whose targets were the ice cream vans of two feuding ice cream manufacturers in the mid 1990s. The battle between the two families erupts into violence, so UCOS decide to track down the bandit and stop the conflict once and for all.

Luke Hanson has recently been released from jail after serving 8 years for setting a fire at his local school in which the caretaker had been severely injured. He was across the country committing another crime at the time and would like the team to reopen the case. This was Jack's last case before retiring to care for his wife, who was the victim of a hit and run driver. Supt. Pullman gets an offer of promotion that she is finding very hard to resist, but it would mean leaving the squad. A woman who claims to be his daughter approaches Gerry, and Brian rekindles an interest in war gaming. In the course of investigating the school fire, Jack learns the identity of the hit-and-run driver and decides to take action.

Jack's finally discovered the identity of the hit-and-run driver who murdered his wife and he is now prepared to risk everything to kill the man responsible: crook Ricky Hanson. Determined that Hanson should meet the same fate as his wife, Jack lies in wait in a pub car park, engine running. Sandra becomes aware of the situation. She acts fast to prevent him confronting his nemesis, but it results in a crash that jeopardises the future of the entire team. With Jack, Gerry and Brian hospitalised, Sandra's forced to accept temporary help at UCOS from the super-efficient DCI Karen Hardwick, a woman who irritates Pullman on every level. As she struggles to keep the truth behind the crash a secret from Strickland, Sandra becomes deeply suspicious that Hardwick's been recruited to spy on her. And with Jack clearly on the edge and suffering temporary memory loss since the crash, Sandra has her work cut out in trying to keep Hardwick in the dark. Threatened by a new face in the office and desperate to prove that they're still a crack team, even from a hospital bed, the boys need a case. When their consultant, Dr Finlay McKenzie, mentions the suspicious death of a patient, Alan White, on their ward 10 years ago, they seize the opportunity to re-investigate, hoping it will hold the team together. But is Jack still in mortal danger from his nemesis?

Sandra's private and professional worlds become intertwined when her mother has a fall that means she needs to go into a care home and her first choice is revealed to be the scene of a suspicious death a year earlier. Jack, Gerry Standing and Brian decide to go undercover at the home.

When an armoured security van is discovered at the bottom of a lake, the team makes a link with the murder of a woman 17 years previously. The husband of the deceased, who owned the company which the van belonged to, seems to be the prime suspect but when he is provided with an alibi, Sandra decides to dive down to examine the vehicle herself and uncovers the murder weapon. However, the killer is about to strike again.

Jack and the team reopen the investigation into the undetermined death of an elderly woman, partly consumed by her hordes of cats, whose decision to leave her estate to her cats sparked a family feud. When the deceased's pets die, her money and property comes back up for grabs, leaving the detectives with no choice but to get to the bottom of her mysterious demise.

The team investigate when the family of Richard Dunne, one of the last men to be hanged in Britain, say he was the victim of a miscarriage of justice due to police corruption.

When Brian's dog finds a body on a common, it prompts two people to confess to murder. But when the body turns out to be over 600 years old, 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 in fact the perpetrators of other killings. Elsewhere, Strickland is rather more keen for them to solve an even more tricky mystery closer to home.

The team reopen a 20-year-old case when a camera and film belonging to a photographic lab assistant murdered in 1987 are found in a Soho pub toilet. New evidence leads the detectives into the dark underside of the modelling world and to the door of a professional footballer. Meanwhile, Brian's erratic behaviour takes an alarming turn and Gerry is less than happy when his daughter Emily joins the team and looks to Sandra as a role model.

Pullman's mother has a stroke, and this event leads Sandra to start asking questions about her father, but she ends up losing her trust in the team when she discovers they have withheld information about her father from her. The revelation that he committed suicide while under investigation for corruption causes the detective to doubt all she took for granted, but she tries to set her feelings aside when she is asked to look into the death of a circus ringmaster who burned to death in his caravan, leaving only his feet behind.

The trial of Ricky Hanson starts, and the members of UCOS are scheduled to appear as witnesses. Hanson is the man who killed Jack Halford's wife, but he's on trial for attempting to murder Jack, who was recovering from a car accident over a year ago. Hanson's barrister is clearly out to discredit each of them individually. While at the courthouse, they are asked by an acquaintance of Jack's, Sam Tallis, to look into the death of Ralph Wheeler, who was killed and left his fortune to a tart named Carrie Soper. As they look into the case, they find several possible suspects, including a solicitor, a doctor, and someone with a lengthy criminal record. In the end, the case revolves around a car accident and organ donation.

With Jack Halford away following the acquittal of Ricky Hanson, Sandra, Gerry and Brian investigate the death of actor Michael Austin, who was shot dead during the performance of a play. The gun was loaded with blanks, but a piece of metal lodged in the barrel killed him. The death was ruled accidental at the time, but Austin's daughter Catherine has recently written a book, and new evidence in the form of a threatening note has come to light. The team is joined by a young officer on the fast track for promotion, James Strickland, the DAC's nephew. They interview Austin's then wife, Helen Brownlow (she's also an actress and the one who fired the gun on stage) and the stage manager, Derek Bennett, as well as Catherine Austin's agent, Mel Simons, who sent the note to her publishers. Forensics indicate that the letter may have been doctored. Meanwhile, the boys have forgotten Sandra's birthday, but she does accept a dinner invitation from the young Strickland.

The UCOS team investigates the death 10 years ago of popular disc jockey Johnny Deacon who died in a fire when the radio station was set alight. The police knew it was arson, but were never able to find enough evidence to charge anyone. Johnny was very opinionated on air and seemed to go out of his way to be offensive at time. He also had a number of female admirers, one of whom may have been stalking him. With Jack having virtually disappeared meanwhile, Sandra finds herself under pressure from DAC Strickland to start interviewing for his replacement. Despite their best efforts, Jack is nowhere to be found.

Brian finally locates Jack who returns to the UCOS team but remains silent about his lengthy absence. The team investigates the death of rock star Andy Fletcher, who supposedly committed suicide in 1975. Gerry speaks to a dying woman who suggests otherwise. She overheard a fight just before his death, and although she reported it to the police after Fletcher was found dead, her information is nowhere to be found in the files. The band's former manager Clive Evans found Andy but doesn't believe there was foul play. The three remaining band members all deny any special knowledge of what happened, but one of them kept Andy's royalties.

After a bent detective is discovered on the force, the UCOS team is tasked with investigating his only unsolved case. In 1998, assistant brewer Graham Thompson was found drowned in a vat of beer at Felspar Breweries. The dead man's girlfriend has always maintained that it wasn't an accident. Everyone concerned, including Sir Freddie Felspar ,says he was a brilliant brewer and a great loss. The original investigator failed to interview either of Sir Freddie's children and son Julian is now the company's Chief Executive. The brewery had won the gold medal for its beer 5 years running but in 1998 they lost to a small brewery that made its reputation on the win. The team now wonder if industrial sabotage may be at the root of the mystery. Meanwhile, Sandra continues to investigate her late father's activities while he was on the job.

At Brian's insistence, the UCOS team investigates a bizarre case from ten years before where a hypnotized woman subsequently killed her husband. Although the woman, Katie Briers, was found not guilty, the magician in question, Billy Carse, had his career ruined. Carse is now dead but as Jack examines the script used to hypnotize the woman, he realizes that there were subliminal messages throughout that led her to kill. The question is who planted the messages and why. They focus on Carse's rival, Brandon Skye. Meanwhile, a disbelieving Gerry allows himself to be hypnotized to prove it can't be done, but afterward no one will tell him what happened.

A new witness comes forward in the murder of 18 year-old Justin King. Justin had been missing for several months before his body was found but the pathologist determined he had been dead for no more than a week. He had also been tortured. Heidi, now 18 herself, tells the police that Justin had been living on a commune and that she saw him a week or so before he died. From all accounts, Justin simply left the commune one day and was never seen again. Sandra isn't buying it however and believes one of the commune's residents was involved in his death. Brian meanwhile is struggling with his alcoholism and may be looking for help.

The UCOS team investigates the death of Eric Trimble, a soldier who was beaten to death in 1991. Their informant tells them that he and Eric, while still in the Army, were part of secret medical experiments that left the survivors paranoid. Their attempts to investigate those experiments come up against a military establishment that puts every possible in their way, including a visit from MI-5. As the investigation continues however, they discover several other possible motives including the fact that Eric was a bully and also gay. The fact that he is black also makes race a possible motive. Meanwhile, Brian continues to struggle with his alcoholism.

Having lapsed into alcoholism, Brian is booked into a rehabilitation clinic run by an order of monks. A chance remark by Father Bernard leads Brian to telephone Sandra late at night to tell her that there was an unexplained death in the clinic nine years previously. To prevent Brian obsessively investigating by himself, the team take up the enquiry into the death of a heroin addict, and infiltrate Gerry into the clinic as a compulsive sex addict. Brian's wife Esther discovers the whole team at the clinic, and is furious, but Sandra persuades her that it is the only way to ease the strain on Brian. By the time Gerry's cover has been blown, the team have discovered that the dead man, Robert Smith, probably took to drugs as a result of post-traumatic stress disorder, after witnessing or even participating in events in the civil wars which followed the break-up of Yugoslavia. They also discover that some of the staff and even the monks at the rehabilitation centre have secrets they wish to conceal or have concealed their origins.

Jack attends the funeral of ex-cop Derek Brooker who went to his grave trying to prove that journalist Peter Edelmann was killed by the American Air Force to stop him exposing an alleged U.F.O. crash, and persuades Sandra to re-open the case. The former Air Base Colonel denies that Peter was ever there, claiming he committed suicide, but local ufologists say that they were present with him and a code, encrypted in a lottery ticket, unlocks his findings. It was a plane crash, the corpses all suspected terrorists illegally abducted by the American government. However the ufologists and another eye-witness, an ex-airman whose café has been set alight by persons unknown, are too frightened to testify and the case remains officially unsolved.

Gerry has a run-in with David Fleeting who he practically accuses of being a pervert before realizing the man is desperately looking for his wife. The only complication is that she is supposed to have died 18 months previously. Fleeting insists that he recently saw her in a crowd and is now convinced that the body of the car crash victim identified by his sister-in-law - he was away on business trip at the time of the accident - was that of someone else. Sandra isn't too keen but agrees on seeking an exhumation. A DNA test reveals the dead woman to be a Turkish immigrant who was reported missing around the same time Fleeting's wife was supposed to have died. As the investigators soon learn, the two cases are connected and not all is as it seems at first glance.

Ex-actress Gloria Gransford draws the team's attention to a clip, posted on the Internet, from a film she made in 1990 called 'Shadow Show', after which the producer Max Stone was stabbed to death and leading lady Eva Roderick disappeared. Director Don Maddox, Gloria's ex-husband, is egotistical and evasive, and the only other surviving crew member from the film - who posted the clip - is found dead. His young boyfriend goes on the run and located Eva, who now has a new identity. A siege situation develops, which Brian defuses.

Five years earlier Dean Scott was found dead of shot-gun wounds and suicide was the verdict. Now ex-hooker Alice Hill tells the team she was at Dean's house at the time and believes he was murdered. Mike Barnes, Dean's shifty partner, rooked his widow Pam and turns out to be an ex-bank robber, who used the loot to start the business. The search switches to the other robbers, one of whom has gone straight and the other - who fought with Dean the night before the death because he was seeing Pam - is under witness protection. The missing loot is found but the fact that Pam and Alice already knew each other complicates the murder theory.

The team meets a girl called Jo, who is heckling Right Wing comedian Ray Harris. Her aunt Sarah Jones and Sarah's partner Daniel disappeared twenty-five years earlier whilst engaged in a campaign against Ray's sexist and racist routines. The pair actually infiltrated an extreme group of Nazi supporters called the Twenty-Fours, which numbered Ray, policeman Frank Paterson and Ricky Hanson who killed Jack's wife. Frank was also undercover,trying, unsuccessfully, to bust Hanson's drug racket but now joins with Sandra to nail Hanson once and for all, with unexpected help from Hanson's son Luke, who has made a shocking discovery about his father. Ricky Hanson is charged with murdering the couple - and, at long last, there is closure for Jack too.

Whilst Strickland's friend Alistair Dudley is entertaining them on his cruiser at a marina, the team see Leanne Sweeting harangue another boat owner Lawrence Fisher. In 2001 a collision between a tug captained by Leanne's father Neville and a cruiser owned by casino boss Grant Milburn collided, killing five people including Milburn. Neville was blamed but Leanne believes Fisher sabotaged Milburn's boat, as they were business rivals. Certainly Fisher profited by the tragedy in business terms. Milburn was going to open another casino and his croupiers were also prostitutes, but the case is altered by the knowledge that Milburn's wife's lover was also on his boat and engaged in a brawl at the crucial moment.

Thirty-three years after the corpse of Dr. Simon Lockhart was found in his butcher's shop at Smithfield the body of Harry Eldridge is discovered - cut into pieces. The doctor used to gamble with Harry and other butchers - now all retired - and Jack discovers from the Lestade brothers, butchers who are Gerry's cousins, that Gerry and other butchers were in the financial clutches of gangster Danny Paye, now in a care home. Brian learns that the doctor performed illegal abortions - anathema to strict Catholic Eldridge - but Sandra gets the biggest shock on finding that she has an illegitimate half-brother, who was adopted by Eldridge's widow, Julia. Unfortunately his DNA is all over Harry's corpse.

Some years after her wealthy father died of a heart attack confronting an intruder - who fled empty-handed - Vicky Anderson asks Sandra and the team to intervene, since clairvoyant Sebastian Carter, having supposedly communed with the dead man, claims he knew the assailant. Sandra is sceptical, feeling Carter is in league with the would-be burglar and using Vicky to get at what he wanted that night. The trail leads to Penny, Vicky's adopted sister, taken in by Anderson after her father died in prison serving a sentence for fraud, and Simon Beswick, the cell-mate, who tells the team he thinks Anderson was also guilty of fraud and the burglar a double-crossed partner-in-crime after the spoils. Sandra is still unsure if Carter is an accomplice or an innocent dupe though, when the case is closed, his interpretation of her father's feelings brings her closer to half-brother Tom.

In 2007 lecturer Richard Symes fell off a roof at the university where he taught and died. An open verdict was recorded but Brian feels that suicide was unlikely as Symes had just taken a whole load of books out of the London Library. Brian loves going undercover at the library ("It smells of books") where he is befriended by the Urquharts, a couple of elderly lecturers who knew the dead man. Symes' widow Paula tells Sandra her husband was regarded as a dinosaur and sacked by vice-chancellor Ventham,but he claims that Symes was stealing books from the university library to sell in Paula's shop,which Paula admits. Her young lover Tim was also part of the racket. Brian works out that the Urquharts are trying to locate one of the books Symes stole,a priceless first edition which he hid somewhere in the London Library. But several other interested parties are also after it - including the murderer.

Sandra does not believe recently released paedophile John Davies when he owns to killing 5-year old Yasser Gorton-Blackledge, who disappeared after going on a Free Palestine march with his left wing parents Anne and Fred in 1985. Now divorced, Anne still campaigns for liberal issues but Fred is a hard right reactionary and misogynist. Davies eventually admits to Sandra that he was bullied into confession by Anthony Vernon, a violent disciple of Fred who once hoped to make his name in journalism from Yasser's case. Another ex-activist, kindly nurse Gillian Withall, adopted a little boy at much the same time that Yasser disappeared and, as Gerry and Brian read through the files MI5 compiled on the Gorton-Blackledges it becomes more than likely to them that Yasser is still alive.

A recent sexual assault on Helen Vestry in her cake shop is identical to two unsolved rapes which occurred ten years earlier at the Pyramid Chocolate factory,run by unpopular Duncan Miller. All the victims were blonde and the attacker smelt strongly of sweat. The team's investigations also uncover a trilogy of seemingly unrelated disasters which befell the factory at the time - the suicide of a female worker,who was not raped,the discovery of a severed finger in a chocolate bar and the prosecution of contract cleaner Alex Close for using illegal immigrants in his work force. As the connection between the three events emerges it seems likely that a murder also took place in the factory,though the rapist is still very much alive.

The team get involved when graffiti claiming 'I Killed Flak' appears around London, Flak being tag artist Danny Tyler, killed four years earlier. He was part of an artist collective the Maze Group which broke up when Danny received patronage to go solo from art lover Sir David Bryant, a fact which caused resentment from others in the group. Gallery owner Sara Hamlyn admits responsibility for the current graffiti, a publicity stunt for her Flak exhibition but draws the team's attention to a theft from her gallery of one of Flak's works before he died. The team are led to believe that Sir David stole it as he needed money and killed Flak during the resultant argument. Another ex-Maze group member Kevin Humphreys has been blackmailing Sir David as a result. But then Bryant's wife Catherine gives Sandra information which puts things in a different light. Brian has all the while been enjoying a following on Twitter as Top Cop 99, a fact which almost puts the case in jeopardy.

Eight years previously clothes designer Ritchie Levene was murdered, stabbed in the neck with a pair of his scissors. For years his ex-wife Sarah has wanted the case reopened and sees her chance when Gerry comes to her for a change in his sartorial image.She suspects Ritchie's younger brother Adrian who assumed control of the fashion company and took it to new heights. Sandra discovers that married Adrian is having an affair with Ritchie's second wife Alison, though they claim it only began some time after Ritchie's death. Then there is Melanie, the nervous P.A. who found Ritchie's body, and Colin Beck, a financier who encouraged Ritchie to invest money in his scheme and also had a motive...

The team is asked by Dawn Abbott to reopen a fourteen year old case of a fire at the Union drinking club, which killed gangster Mark Johnson and three staff members. It was thought to be an accident but Mark told Dawn days before the fire that he thought somebody was out to kill him. Mark's brother Danny resents any suggestion that he was involved but fire investigator George Mackie tells the team that he thought at the time that the blaze was suspicious and the widow of the painter whose materials were supposedly to blame for the fire recalls that he was handsomely paid soon afterwards. Ultimately the culprit proves not to be a person with a grudge but a serial arsonist hoping to get away with as many fires as possible.

Would-be Euro MP Fintan MacEntee, a former member of the Irish Republican Front, approaches Sandra regarding Barbara, teen-aged daughter of a wealthy arms manufacturer Kenneth Linden-Warner, who was kidnapped in 1983 and, though the ransom was paid, was never seen again. At the time the Front admitted responsibility but MacEntee now claims that it was purely a publicity move and the Front never took Barbara. Sandra's belief that it was an inside job is confirmed when it is discovered that Barbara's brother Michael, who did not get on with his father, shared a squat with MacEntee and helped him prepare the ransom note to get money from his father. Barbara had also rowed with boy-friend Greg Hampton, now married to Barbara's supposed rival but in fact anything but. The family did indeed have secrets and Miss Jones, Linden-Warner's loyal former secretary, knows all of them as well as the actual fate of Barbara.

In 1999 promising young boxer Eddie Mayfair was shot dead but his rival in the ring and chief suspect Milton Joseph had an alibi and other likely suspects have all since died or disappeared. Now the murder weapon has been found at last. Eddie's widowed mother has moved in with his former agent Harry Gallo and his old sweetheart married his sparring partner Danny. Jack discovers that Eddie was in a rival street-gang to Milton, long before they met in the ring and Milton's gang members were the men who have now all disappeared. The biggest breakthrough, however, occurs with the knowledge that Eddie was meant to throw the fight with Milton as certain people had money on that result - the same people who killed Eddie to stop him talking.

Detective inspector Frank Paterson joins the team to reopen a thirty year old bullion robbery after he has tracked down the getaway car. Two guards died, allegedly at the hands of vicious Michael Denby - the fourth man in the robbery, who, unlike the other three, was never accounted for and is still at large. Frank and Sandra do not get on and she is sceptical when he claims that John Felsham, now a deputy assistant commissioner, was a bent copper who tipped Denby off, Felsham telling her that Frank has long held a personal grudge against him. However Felsham arrives unexpectedly at a back street pub once used by Denby where Frank and Gerry are following a lead and Frank fights him. As a result Felsham wants UCOS disbanded. But the team are determined to carry on and, backed by Strickland, they make sure that they get their man.

The team investigates the death of a renown paleontologist.

The team investigates the murder of an anonymous tramp on a London Underground train 15 years earlier.

The UCOS team are drawn into a world of immigration, Albanian gangs and family feuds when they reinvestigate the death of an unidentified man.

The UCOS team reinvestigates a highly sensitive case when new information links an unexplained death to a series of drug rapes in East London.

Psychologist Samantha Gerson comes to UCOS to carry out a work study on older men. However she also wants the team to look into a suspicious hit and run from six years earlier, the victim being her brother Darren, a cycle courier. Darren suffered memory loss but now as his memory returns, he recalls that the package he was carrying was stolen and suspects foul play. His client - and lover - Claudia Scott, imported Moroccan furniture and Jack suspects a drug connection but Darren was also the founder of GLS, an anarchist group committed to ridding London of cars. When Darren is murdered the UCOS team have to find out how he funded GLS and who wanted him silenced.

Some past memories and feelings are stirred up when Detective Superintendent Sandra Pullman is reunited with an old flame, DCI James Larson.

In 2004 physics professor Philip MacKenna was apparently abducted from a Paris-bound train. His journey was last minute, after a colleague was robbed, and witnesses at the time proved to be using false identities, suggesting a plot to kidnap him for his expertise. Now his wife is getting cryptic emails, impossible to trace, suggesting he is alive, but she has been holding back a secret. A tip off from a Whitehall mandarin leads the team closer to the truth.

Stephanie Parr tells the team that her biker boyfriend Reese Chapman, as a rite of passage, must kill a rival gang leader who supposedly murdered his father Eddie, founder of the violent criminal Braves biker gang when she is sure the killer was Marcus York, the club's current president. Superintendent Barlow asks the team to back off as he is surveying the Brave for drug-peddling but when Stephanie is attacked Sandra resolves to continue, despite a lack of witnesses for fear of York and Barlow's unhelpful attitude. David, Stephanie's father, holds the key but the identity of the killer does Barlow no good.

A website highlighting unexplained disappearances alerts the team to the death of young mechanic Christopher Collins seven years earlier. Sandra discovers he was really called Tommy Barton, and was on a witness protection scheme having testified against drugs baron Derek Robinson. He was, though, a drug smuggler himself and was having an affair with his boss's wife. In tracing the killer the team is much aided by the hypnotherapist treating Brian's insomnia and they also learn that UCOS will not be terminated to save money.

When keeper Zac Halsey's corpse was found in the tiger enclosure at Harefield Zoo in 2006, the assumption was that he had been mauled to death, but blood found during the refurbishment of his flat now suggests that he was murdered and his body dumped in the compound. He had recently been to Spain where the knife that killed him was purchased. An animal rights campaigner, sacked security guard and a couple with whom Zac enjoyed extreme sports, are all suspects and all seemed to have been in the zoo the night Zac died. Jack works out the killer's identity even though it means he and the team miss his presentation for bravery as a result.

The team is less than pleased when arrogant civil servant Stephen Fisher coerces them into investigating the murder - in 1851 - of Abigail Padua, a mathematical expert whose death led to the collapse of her family business and a widespread financial crisis. With no living witnesses and a different geography to the time the team must pore over the original statements to prove that the killer was a witness who lied to the police. However, they, with Strickland's backing, have another mystery on their hands - Fisher's obsession with cracking the case, which itself could have far-reaching effects in the modern business world. Jack however is able to thwart Fisher before he leaves the unit for good to spend his last days in France.

Seventeen years earlier Sandra's first case involved the disappearance, never resolved, of music student Lesley Hewitt and now Lesley's sister Emma has been sent a photo of Lesley walking in a park just before she vanished. Sandra believes that a jogger in the picture was a serial killer responsible for the deaths of other young girls, possibly working with a female accomplice as Emma says that Lesley was offered a gig before she vanished. Ex-model Annie Banks and bookshop owner Stuart McKelvie are also in the photo, taken by Greg Banks, a recently deceased photographer whose studio contains several pictures of women who were abducted and killed. Annie and Stuart initially claim not to know each other but Sandra breaks down their stories and discovers that Annie knows who the jogger is. After concluding the case Sandra leaves UCOS to work with Max Clement.

The team is less than pleased when arrogant civil servant Stephen Fisher coerces them into investigating the murder - in 1851 - of Abigail Padua, a mathematical expert whose death led to the collapse of her family business and a widespread financial crisis. With no living witnesses and a different geography to the time the team must pore over the original statements to prove that the killer was a witness who lied to the police. However, they, with Strickland's backing, have another mystery on their hands - Fisher's obsession with cracking the case, which itself could have far-reaching effects in the modern business world. Jack however is able to thwart Fisher before he leaves the unit for good to spend his last days in France.

A young woman insists that the suspicious death of a local librarian was because of witchcraft, and the team are drawn into the world of magic and the supernatural. A series of strange events occur, and they are put under increasing pressure. The squad become convinced that the supernatural exists and struggle to remain cynical.

The team investigate the disappearance of an attractive young mum and her six-month old son in the 1970s. They also have to submit to a physical and psychological assessment.

The trial of Ricky Hanson starts, and the members of UCOS are scheduled to appear as witnesses. Hanson is the man who killed Jack Halford's wife, but he's on trial for attempting to murder Jack, who was recovering from a car accident over a year ago. Hanson's barrister is clearly out to discredit each of them individually. While at the courthouse, they are asked by an acquaintance of Jack's, Sam Tallis, to look into the death of Ralph Wheeler, who was killed and left his fortune to a tart named Carrie Soper. As they look into the case, they find several possible suspects, including a solicitor, a doctor, and someone with a lengthy criminal record. In the end, the case revolves around a car accident and organ donation.

Pullman's mother has a stroke, and this event leads Sandra to start asking questions about her father, but she ends up losing her trust in the team when she discovers they have withheld information about her father from her. The revelation that he committed suicide while under investigation for corruption causes the detective to doubt all she took for granted, but she tries to set her feelings aside when she is asked to look into the death of a circus ringmaster who burned to death in his caravan, leaving only his feet behind.

The UCOS team are drawn into a world of immigration, Albanian gangs and family feuds when they reinvestigate the death of an unidentified man.

The vicious criminal Chopper Hadley, who has been back in the country for a week, is searched for by the team. However, Halford is viciously intimidated and the squad start to realise the full danger of their target. Desperate measures are used and Brian is sent undercover to get Hadley once and for all.

In 1999 promising young boxer Eddie Mayfair was shot dead but his rival in the ring and chief suspect Milton Joseph had an alibi and other likely suspects have all since died or disappeared. Now the murder weapon has been found at last. Eddie's widowed mother has moved in with his former agent Harry Gallo and his old sweetheart married his sparring partner Danny. Jack discovers that Eddie was in a rival street-gang to Milton, long before they met in the ring and Milton's gang members were the men who have now all disappeared. The biggest breakthrough, however, occurs with the knowledge that Eddie was meant to throw the fight with Milton as certain people had money on that result - the same people who killed Eddie to stop him talking.

The team investigates the murder of an anonymous tramp on a London Underground train 15 years earlier.

Would-be Euro MP Fintan MacEntee, a former member of the Irish Republican Front, approaches Sandra regarding Barbara, teen-aged daughter of a wealthy arms manufacturer Kenneth Linden-Warner, who was kidnapped in 1983 and, though the ransom was paid, was never seen again. At the time the Front admitted responsibility but MacEntee now claims that it was purely a publicity move and the Front never took Barbara. Sandra's belief that it was an inside job is confirmed when it is discovered that Barbara's brother Michael, who did not get on with his father, shared a squat with MacEntee and helped him prepare the ransom note to get money from his father. Barbara had also rowed with boy-friend Greg Hampton, now married to Barbara's supposed rival but in fact anything but. The family did indeed have secrets and Miss Jones, Linden-Warner's loyal former secretary, knows all of them as well as the actual fate of Barbara.