A gigantic white stallion appears mysteriously to a Traveller grandfather and his two grandsons in an Irish slum. Since, puzzlingly, the younger of the two boys is the only individual who can control the horse, ownership falls to him and his older brother by default. There being no place for the animal, they move him into the apartment of their alcoholic Traveller father. Police remove him and, in a shady deal, he ends up under control of a wealthy, underhanded horse breeder. The boys manage to retrieve him and escape on his back, but the stallion seems to have his own travelling agenda.

The film Ossie is watching in the cinema is Back to the Future Part III (1990).

Ossie:
What's his name?


Grandfather:
He's called Tír na nÓg.


Ossie:
But why's he called that?


Grandfather:
Because he came from a land under the sea.

Continuity: The photograph of Mary Riley shown at the beginning is larger and more widely framed (showing much of the front of her caravan) than the "same" picture shown at the end (showing only Mary and her baby in the door).