The Cartwrights challenge an arrogant and cruel British prizefighter, the Duke, and his alcoholic manager to a bout with John Heenan (the Benicia Boy), after the Cartwrights' meek friend J.D. gets pulverized by the Duke in a bar-fight. J.D. is adored by saloon girl Marge, but he has been too shy to return her affections. While the Cartwrights wait to see if Heenan will actually take the bout and come from San Francisco, the Duke pursues Marge and assaults her when she rebuffs him. When the manager comes to Marge's rescue, he too is beaten up by the Duke (who, it turns out, is the manager's brother). Infuriated by all this, Hoss Cartwright himself challenges the Duke, and knocks him out in the fourth round of a bare-knuckle fight refereed by Sheriff Roy Coffee. The Duke and his brother-manager reconcile in the humility of defeat, then learn that the Benicia Boy will accept the proposed bout, but only the Duke comes to San Francisco. The Duke apologizes to all he has offended while in Virginia City and heads west to fight Heenan.