Ordinary men and women are recruited to turn the tide on illegal drug smuggling in the early 1990s Britain in a gripping six-part drama inspired by an untold true story. The Thatcher government is losing the war with the drugs gangs and Her Majesty's Customs and Excise needs to think outside the box to turn the tide. Bureaucrat Blake (Douglas Hodge) agrees to an outlandish idea: a top-secret training programme for normal Customs employees to go undercover and infiltrate Britain's most dangerous drug cartels. They will be given only basic training to build new identities - their so-called legends - incorporating some of their real lives to help them retain facts and figures. Working under the leadership of Don (Steve Coogan), nervous recruits Bailey (Aml Ameen), Carter (Tom Hughes), Erin (Jasmine Blackborow), Guy (Tom Burke) and Kate (Hayley Squires) prepare to take the starring roles in one of the most remarkable criminal investigations conducted.