The future of the ranch is jeopardized when bandits steal a prize bull and breeding stock which Billy Blue Cannon and Manolito Montoya have bought in Mexico with the last of the Cannon money. Victoria persuades husband John Cannon to send the boys to her father's rancho for the cattle after his brother Buck Cannon is injured. Manolito bargains with his father, Don Sebastian Montoya, for his second best bull. Don Sebastian thinks the boys are pulling a prank and hires bandits to steal the bull. They boys make a desperate attempt to catch the thieves and still prove their trustworthiness.
