The Grey Mare

"Listen. Mari Lwyd. White as moonlight. Rattle-bagged and broken backed. Steed of winter who the pale men carry.

"Who are those that squire you? Slow and ceaseless, yard by yard, house by house, and door by door."

The Mari Lwyd is a fine Welsh Christmas Tradition - the skeleton of a horse roams the streets, begging to be let in for food and warmth. Once she knocks, only the most cunning can send her away.

Ianto Jones has come to a remote village for a quiet Christmas. But the Mari Lwyd has come knocking. And she's real.