Fergus, an IRA foot soldier, is part of a small group led by ferocious idealogues Jude and Maguire. They kidnap a British soldier, Jody, in Northern Ireland and attempt to exchange him for a group of imprisoned IRA members. As the tense and exhausted comrades take turns guarding Jody, a tentative friendship forms between Fergus and the frightened captive. Aware of his colleagues' growing contempt for what they perceive to be a weakness on his part, Fergus pointedly accepts the task of killing their captive when it becomes apparent that British officials will not comply with their demands. As Fergus marches Jody into the woods at gunpoint, the prisoner gets away, only to run into a road and be run over by a British armored car. Fergus escapes, leaving Maguire and Jude trapped in a hail of gunfire.
Fergus flees Ireland and melts into London's underground of undocumented Irish workers. Haunted by the memory of Jody, he looks up the dead man's lover, Dil. Alternately seductive and petulant, desperately needy and infuriatingly aloof, Dil soon has Fergus bewitched. But Fergus is tormented by his past and, as their relationship grows ever more intimate, tortured by the fact that he has an entire other life of which she is unaware. Still, it's Fergus who's in for the biggest shock, when he learns Dil has an even more surprising secret. Things are further complicated by the unexpected re-appearance of Jude and Maguire, who insist Fergus help them with one last assassination.