Mark Lane and Reg Bachelor work as ranch hands in Wyoming in the summer, then head south before winter sets in. As the men move farther and farther south, they come onto the Navajo Reservation where they're hired to trap wild horses in Mexico. As they prepare a headquarters in the small village of St. Theresa which borders on the vast Calderon land grant, they're completely unaware that they've settled into a place from which gringos have been known to disappear...