In 2006, Northern Ireland's bloody Troubles had dragged on for decades. Now with the growing threat of a new generation inspired by the 9/11 attacks to escalate the conflict to new levels of destruction, the Catholic Republican and the Protestant Unionist sides are finally persuaded to seriously explore a peace agreement at U.K. Prime Minister Tony Blair's (Toby Stephens') urging. Unfortunately, the principle negotiators, firebrand Democratic Unionist Party leader Ian Paisley (Timothy Spall) and Sinn Fein politician Martin McGuinness (Colm Meaney), are decades-long implacable enemies. However, with talks about to start, Paisley has his wedding anniversary that he is determined to attend at home, and McGuinness decides he must accompany his enemy to prevent him from being persuaded to abandon this chance for peace. With Prime Minister Blair and his MI5 staff nervously watching from secret cameras, the two foes undertake a journey together in which they bridge the seemingly unbridgeable and change the course of history.