Thanks to a sleeping draught that she had her loyal Sinaguas throw into the fire of their bivouac, the witch Zhenda imprisons the pards in the Grand Canyon, where the primitive tribe subdued by her has its refuge. And while Tiger Jack starts out with a squad of Navajos in aid of his friends, Sagua rebels against his mother, guilty of his wife’s death, and frees Tex, Carson and Kit. The three of them thus escape along an underground labyrinth, where they face a herd of ferocious monitor lizards that populate a lost forest, and see the light again just moments before diving into the Colorado!