In 1920s Ireland young doctor Damien O'Donovan prepares to depart for a new job in a London hospital. As he says his goodbyes at a friend's farm, British Black and Tans arrive, and a young man is killed. Damien joins his brother Teddy in the Irish Republican Army, but political events are soon set in motion that tear the brothers apart.
In Ireland, American lawyer Ingrid Jessner and her activist partner, Paul Sullivan, struggle to uncover atrocities committed by the British government against the Northern Irish during the "Troubles." But when Sullivan is assassinated in the streets, Jessner teams up with Peter Kerrigan, a British investigator acting against the will of his own government, and struggles to uncover a conspiracy that may even implicate one of Kerrigan's colleagues.
Michael Collins plays a crucial role in the establishment of the Irish Free State in the 1920s, but becomes vilified by those hoping to create a completely independent Irish republic.