 Billy Simpson is a shady boxing promoter in South London banned from legitimate fights. It s the biggest day of his life, though, because he has a champion on his hands, his 20-year-old son, Eddie. Billy s put all his money on a victory, as have his quarreling daughters. But Eddie is nervous, an odd guy in a cap is hanging about, the licensed promoter Billy has hired to arrange the evening s other fights has hired dogs, the manager of Eddie s opponent looks down scornfully on Billy and on South London, and Scotland Yard wants to Billy in gaol for the death of a club brawler. When the night goes disastrously wrong, Billy tries to find out who double-crossed him.