Santo vs. the Headhunters aka Santo contra los cazadores de cabezas sees Santo not as a wrestler this time but instead as a big guy in a silver mask who has a couple of fights, including a fight with four men at the start of the movie. The police arrive and arrest three of the thugs, but the ringleader–whom Santo identifies as the foreign leader of a drug-smuggling gang–manages to escape, leaving behind a bamboo dagger.
This is the same type of dagger that wealthy explorer Alonso Grijalva is telling a group of friends was used by the Jivaro indians to cut off the heads of their enemies: he shows them a shrunken head to make his point.
Meanwhile, the man who had fought Santo, Tirso, is back in the Amazon jungles. He tries to convince the chief of a tribe of Jivaros to stop going to war with other tribes and instead unite to fight the whites. The Jivaros are the descendants of the Incas, who had their empire stolen by the Spaniards. In revenge, Tirso suggests that they kidnap Mariana, don Alonso’s daughter, and sacrifice her to the gods.
Mariana receives a large golden amulet in the mail and later, a black orchid and some emeralds turn up. Alonso consults with Professor Castro, who agrees that Mariana has been chosen to be the “Bride of the Sun.” The natives shower her with riches and then, at the full moon, sacrifice her. Castro contacts Santo by radio, but Santo says he has to travel to London and can’t arrive for three days.
By the time Santo lands his light plane in South America and meets Castro, it’s too late: Mariana has been kidnaped, through the treachery of Husca, Alonso’s long-time butler who turns out to have been a Jivaro “mole.” Santo, Alonso, Carlos, and Prof. Castro lead an expedition to rescue her.
Now the long walk begins. During the trek Santo and his friends are menaced by alligators, jaguars, vampire bats, electric eels, Jivaro warriors, and traitors from within their own group – most of which are wrestled by Santo at some point!
Finally, only Santo, Carlos, and Alonso are left alive. They reach the Jivaro village just as the ceremony is beginning: a fight breaks out. Husca is killed by one of his own warriors for threatening to stab the sacred Mariana. Santo defeats the chief but spares his life, earning their free passage to safety; when Tirso tries to intervene, Santo tosses a spear and puts an end to his villainy. Santo, Alonso, Carlos and Mariana return to civilization.