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?

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.

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.

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.

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 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.

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?