The second two-parter sees DS Annie Cobbot investigating the murder of a woman found on moors, while DCI Alan Banks is called in when the body of a teenage girl is discovered in a storage room down an alleyway. The final two episodes see Banks drawn into the criminal underworld of Soho when he reluctantly accepts an unofficial request from Chief Superintendent Rydell to find his missing daughter.
In Season 2, new recruit Helen Morton finds evidence linking Banks to a murder victim, an accountant is killed by a hitman and the team are called to investigate the murder of a teenager.
In Season 3, two people claiming to be social workers take away a woman's son, the body of a journalist is found and Helen leads a firearms team to retrieve a gun from a teenager's bedroom.
In Season 4, the team uncovers a dark world of vice in a town where nobody wants to talk, a lawyer's body is washed up by an underground river and a student's body is found in a ravine.