When old traveller Grandpa Ward relates the legend of Tir na nOg to his grandsons Ossie and Tito, little does he know the chain of events he sets in motion. Ossie and Tito are the sons of Papa Riley (Gabriel Byrne), a Traveller King who has rejected his tribe and nomadic roots to settle with his children amid the grim tower blocks of Dublin.

Then Grandpa Ward one day returns from his travels with a magnificent white horse which has followed him home, a horse named Tir na nOg which becomes curiously attached to Ossie and Tito, and they to it. But it soon attracts the unwanted attentions of an unscrupulous horse stud owner who acquires Tir na nOg illegally.Devastated, Ossie and Tito – driven by their love for the horse – steal him back and make their break for freedom into the Irish countryside – with a $5,000 reward on their heads and the police force hot on their heels.

Papa Riley must set off after Ossie and Tito on the journey of a lifetime, a journey from which neither he or his sons will ever return…a journey into the west