La montagna misteriosa

In a secret valley inside the extinct volcano called Mount of the Vultures lives a colony of Aztec survivors who for generations have enslaved a tribe of Pima Indians to make regular sacrifices to the Sun God . This time they chose the daughter of the Pima chief and a boy from the outside world: Kit Willer . However, they have come to terms without the two fathers: a Tex determined to do everything and a slave leader now ready to rebel, who, supported by a "reformist" faction of Aztecs, will leave no stone unturned to save the two boys and overthrow the tyrannical rule of the High Priest.

This adventure is the latest in what we might call Kit Willer's "teaching cycle," a series of stories that saw father and son touring the American Southwest together.