Based on a controversial true story, Martin McGartland (Jim Sturgess) decides to become a British undercover informant in 1980 to spy on the Irish Republican Army. Due to his undercover work Martin is forced to lead a double life. If he tells his family about his real status, they will all end up getting killed. Things start to go awry when the British police exposes Martins undercover mission. He gets taken captive by the I.R.A. but manages to escape the torture. Martin McGartland is still hiding today.