Based on the novel "The Heritage of Michael Flaherty" by Colin Leinster, "The Outsider" tells the story of a Vietnam veteran brought up in an affluent Irish American family who travels to Northern Ireland to volunteer for the Irish Republican Army. The inspiration behind this move comes after hearing his grandfather's heroic anecdotes.

The American becomes a victim in the "troubles" and is framed for a murder, leaving both the IRA and the British forces wanting him dead.