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.

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.