As the police infiltrate a gang of identity thieves, Leo faces a choice between justice and revenge.

When his wife and teenage daughter are involved in a hit-and-run car crash, Leo begins a painful journey back to his native Sheffield.

The team is drawn into the investigation of a series of brutal, apparently motiveless murders in the academic world.

Nikki's beliefs are put to the test as she realises they are facing murders that are committed for sheer pleasure.

Harry discovers Nazim's death may not have been suicide. Is Dr Sanders the culprit? Meanwhile Leo investigates the murder of a bank manager.

The team is called to a drive-by shooting outside a London nightclub. They arrive to a scene of carnage with several people dead, or dying.

The man behind the bloodshed pits both factions against one another and the team are in a race against time.

A paranoid schizophrenic goes on a violent frenzy in a busy high street. When a young man from the same care home commits suicide, Nikki is convinced there is a connection.