Season 4

When DCI Janet Chambers (Connie Hyde) goes into labor, Commander Clare Blake takes charge of the investigation into the death of a two-year-old girl found on the site of a now abandoned psychiatric institute. The girl has been dead for several years, but her body had been stored in a tightly sealed drum and is well preserved as a result. She also has a cross branded onto her chest. The pathologist's report is inconclusive, so the team start to check medical records of former patients.

Eric Thornton and John Littlewood figure prominently in hospital files, but when it's confirmed that Littlewood has died, the police focus all their effort on Thornton. A dark history of mental problems and violence related to them, Thornton stands out as the prime suspect in the girl's murder, but when his own mother (Celia Imrie) is murdered in cold blood, James isn't convinced that Thornton is responsible for either death.

The body of a self-made millionaire is found floating in his swimming pool two days after he was arrested by the Serious Fraud Office, having been siphoning funds to fund a lavish lifestyle with a wife and two mistresses. Commissioner Branton asks Blake to oversee the investigation into the death. DCI James soon discovers that the women knew all about about each other, and believes that each had a motive for murder.

A post mortem examination shows that Donald Griffith died from a blow to the neck, and not by drowning, supporting DCI James's theory that one or other of the women in his life had decided to profit from his death. Dutch detective Van Hauten arrives with a possible solution, and designs on Commander Blake.

A priest is brutally beaten and stabbed to death on an east London estate, where bad feeling between residents and police threatens to undermine the investigation. Suspicion falls on local boxing protege Jimmy Bannerman, but progress is hampered when Doug and Clare demonstrate very different attitudes to the brutal competitiveness of the sport. However, a vicious attack on a fellow detective forces them to form a united front. Boxer-turned-actor Gary Stretch stars as Bannerman's…

As the investigation continues, suspicion shifts from Jimmy Bannerman to Terry Donnolly when an eyewitness puts him at the scene of the murder and information on his troubled childhood comes to light. Doug has been coping with his own emotional events at home, but realises he may already know who the real killer could be.