An Irish boxer, Sean Kelleher, who accidentally kills his friend in the ring and promises his wife that he will never box again. However, years later, when he discovers that his only son is dying of the same hereditary heart disorder which has taken his wife, he is forced to break his promise in order to raise the substantial funds needed for the surgery that could save his son's life. Now gone past his prime, he is forced to the underground world of bare knuckle fighting.