All eight episodes of the BBC crime drama following an undercover team of law enforcers. After leading a botched drugs bust, HM Revenue and Customs officer Marcus 'Ash' Ashton (O.T. Fagbenle) is chosen to head the new top-secret law enforcement squad known as the UNIT (Undercover Narcotics Intelligence Team) and is tasked with taking down key members of the criminal underworld. While Ash uses his knowledge of the street to fulfill his long-time goal of capturing high-level crime bosses and drug dealers, the team close in on their top target, notorious crook Roach (Trevor Eve).

Harry Verma, an immigration solicitor nursing a sick father and a gambling habit, has taken to legal aid fraud and Sean Carlisle, collaring illegal immigrants for a living, is self-destructing on pills and booze. But once brought together, the two men team up for the blag of their lives.