American draft dodger Kevin (Joseph Kaufmann) and his hippie girl friend Terry (Jennifer Billingsley) are hitchhiking along a rural road in the mountains of north-central Mexico when they encounter Wicks (Alex Rocco), a middle-aged American who heads a band of mercenary soldiers and invites them to his headquarters. After they arrive at Wicks's encampment, he starts to molest Terry, and when Kevin tries to intervene, he is badly beaten. Kevin is able to escape to try and find help while Wicks and the other men fight over Terry, whom they intend to make a slave.At the nearby town of San Christobal, Kevin is unsuccessful in trying to persuade the local sheriff Alvarez (Joseph Bernard) and the frightened townspeople into helping him fight the mercenaries. By the time Kevin returns to Wicks's headquarters, Terry has been raped by Wicks and a succession of his men. Seeing Terry stripped, with a noose around her neck and carrying water to Wicks, Kevin becomes enraged and murders him. With the help of Ross (Paul Carr), one of Wicks's now disillusioned men, Terry and Kevin are able to flee, but when the rest of the mercenaries discover Wicks's corpse, they chase the trio through the desert.At the climax, a large firefight happens when the mercenaries, now led by Wicks's successor, the Colonel, take on Kevin and Ross in the desert where the mercenary thugs are killed one by one. But Ross is killed in the shootout and just when Kevin takes on and fatally wounds the Colonel, he shoots and kills Kevin. Terry, takes an assault rifle and kills the Colonel. With all of the men, including Kevin being dead, Terry wonders off alone, now stranded in the desert.