The novel is set in Ireland in the era of political upheaval between the 1916 Easter Rising and the eventual truce signed with the United Kingdom in 1921, seen through the eyes of young Henry Smart, from his childhood to early twenties. Henry, as a member of the Irish Citizen Army, becomes personally acquainted with several historical characters, including Patrick Pearse, James Connolly and Michael Collins. Energized by Sinn Féin's victory in the General Election of 1918 and the party's establishment of the independent Irish Republic, Henry participates in the Soloheadbeg Ambush, the first engagement of the Irish War of Independence, as a lookout.
Later, he becomes a gunman in the ensuing guerilla war against the British, setting barracks on fire, shooting G-men and training others to do the same. At the end of the novel, Henry comes to think that the endless violence and killing of innocent people has little to do with the concept of a free Ireland, or the prospect of a better life in Ireland and more about personal gain.