In 1867, three British colonies became the four provinces of the new Dominion of Canada. Among the Fathers of Confederation was D'Arcy McGee, a fiery former Irish nationalist and friend of John A. Macdonald. As the fledgling country was forming, its security was threatened by the Fenian Brotherhood, a group of Irish republicans that advocated a forcible takeover of Canada by the United States. Conor O'Dea, a young Irish Catholic with political aspirations, who is the assistant to D'Arcy McGee, becomes romantically involved with a young Protestant woman, which provokes upset and violence. When McGee is assassinated by a Fenian sympathizer - or so everyone believes - O'Dea takes it upon himself to discover the real assassin, and to prevent the prime minister of Canada, Sir John himself, from being the next victim.