On their first day of training with the Metropolitan Police, new recruits Jamie, Bunny and Tina are asked to join a team of undercover detectives, a secret unit involved in the long-term penetration of criminal gangs. Their target? One of the world's biggest drug dealers: Den Donovan, alias 'Tango One'. To close in on their quarry, the three must go back into the outside world and become criminals themselves. But someone within the Met is pursuing an alternative agenda. Someone who has deliberately put their lives on the line…