When half-breed Indian Yaqui Joe robs an Arizona bank, he is pursued by dogged lawman Lyedecker. Fleeing to Mexico, Joe is imprisoned by General Verdugo, who is waging a war against the Yaqui Indians. When Lyedecker attempts to intervene, he is thrown into prison as well. Working together, the two escape and take refuge in the hills, where Lyedecker meets beautiful Yaqui freedom fighter Sarita and begins to question his allegiances.

Professor Challenger leads an expedition of scientists and adventurers to a remote plateau deep in the Amazonian jungle to verify his claim that dinosaurs still live there.