The film follows Frankie McGuire (Pitt), a top soldier for the Provisional Irish Republican Army (IRA) who travels to New York City under the alias Rory Devaney. His secret mission is to purchase anti-aircraft missiles to use against British helicopters in Northern Ireland.
Through an IRA sympathizer, Frankie is housed with Tom O'Meara (Ford), a veteran Irish-American NYPD sergeant who has no idea of Frankie's true identity. As the two men form a close, father-son bond, Tom eventually discovers Frankie's secrets, leading to a direct moral and physical conflict.