Arizona, 1869. Winnetou and Old Shatterhand try to put an end to the practices of the unscrupulous Colonel Brinkley, who is terrorizing the prairie with his gang of outlaws. The blood brothers are also worried about Winnetou's rebellious sister Nscho-tschi, who does not behave like a squaw but prefers to hunt like the men. Bobby, an orphan boy from New York, and his best friend, Rat Winchester, arrive in the Wild West with a map of a hidden gold treasure in their pockets. When Brinkley learns of their secret, he kidnaps Bobby and Nscho-tschi and steals the map. Winnetou and Old Shatterhand set off in pursuit, and Bobby experiences the adventure of a lifetime. Can the friends defeat the bandits and find the legendary treasure of Silver Lake?