Belfast, 1974. Two Ulstermen, two sides. On one, British Army bomb-disposal officer Marcus Richardson; on the other, Davy MacCutcheon, Provisional IRA armourer who has been constructing bombs since his teens. After he is nearly killed by a car bomb, Marcus accepts an undercover mission to infiltrate the Falls Road ghetto, join the Provisional IRA, and expose their bomb-maker. When Davy sees his devices used to maim and kill innocent people rather than military targets, the bomb-maker begins to question what he's doing. His request to be discharged is countered by an order that he go on one last mission. The paths of the two men cross in an abandoned farmhouse in the middle of a plot to kill the British Prime Minister.