Maria San Carlos, the only daughter of a wealthy landowner, is betrothed to Escobar, a General in the Mexican Revolution, but she does not love him. Escobar sends a mixed gang of Americans and Mexicans to capture her and bring her to him. Complications ensue when an American cowboy, who had been hitching a ride with Maria's entourage and has his gold stolen by the gang, pursues them across the desert.

Arácnea's residents have been desperately searching for a source of food to save the life of their queen (a big spider). Earth is chosen, since human brains are apparently like health food for alien spiders.