The Silers' gang is chasing Apache Chief Winnetou and his sister Nscho-chi, after having killed several Apaches to steal their horses. Winnetou and his sister run into a group of trappers led by Old Firehand. The trappers help Winnetou and his sister Nscho-chi evade the Silers' gang. Together, they head for the border town of Miramonte. In Miramonte, the Mexican Sergeant Mendozza and his men have captured and imprisoned Billy-Bob Silers, the young brother of the Silers' gang leader. The locals fear an attack by Silers' gang that wants to free Billy-Bob. But Sergeant Mendozza refuses to release the bandit's brother. Also in town are Old Firehand's former girlfriend Michèle Mercier and her son Jace Mercier. When they meet in town, they're surprised but happy to meet again. Old Firehand wants Michèle back in his life but she's reluctant to be involved with a trapper whose life-style is more wild than settled. When Michèle accidentally reveals that her son is also Old Firehand's son, they all rejoice at the news. But the happy moments soon are overshadowed by grimmer news of the impending attack by Silers' gang against the town. Winnetou and Old Firehand offer their assistance to Sergeant Mendozza in organizing the town's defenses.