Sean Kelleher (Michael Madsen) is single father living with his son Michael Kelleher (Luke Whelton) in a small town in Ireland. He was a boxer previously and had caused the death of his friend by mistake in the boxing ring. When his wife was dying years later, she had made him promise that he will never box again. Now his son is dying of a hereditary heart disease and he needs money to keep him alive. They lose their house but to get enough money for a life saving operation Sean has to break his promise and box against the Smasher (Vinnie Jones) in an underground boxing ring.