In the third chapter of Zorro's Fighting Legion, our masked, whip-wielding hero (Reed Hadley) manages to save his friend Ramon (William Corson) just before the old mission explodes. Assigned to trail a couple of Don del Oro's henchmen, Zorro's servant Juan (Budd Buster) discovers a secret room in the Mendolito Mine, where Gonzales (Edmund Cobb) and his men are manufacturing the golden arrows used by Tarmac (Joe Molina) and his Yaquis to terrorize the area.