During the early 1940s, young Mateo's favorite pastime is exploring the mountains near his home. He and his friends have heard the rumors about the seven mysterious cities of Cibola where the walls and streets are covered with gold and gemstones and Aztlan, the ancestral homeland of the Aztec. The friends intend to find the treasures buried within the lost cities. Seeking to escape the poverty in his small ranching community, Mateo continues to search the mountains at every opportunity, and he narrowly escapes dying there after finding what he imagines are veins of gemstones and other precious minerals. He also finds a grotto with a strange obelisk and several mummy-like individuals. Since his best friend, Modesto, has moved to California, Mateo confides in the village blacksmith, an old man who has been there for more years than people care to remember. But a greedy villager overhears their conversation, and that person becomes Mateo's mortal enemy.