The film begins with a raid on a Colombian emerald mine. A gang of crooks, led by female wrestler Alicia (Elsa Cardenas), steals the huge "Cruz del sur" emerald. They have been hired by the mysterious "Gran Desconocido" (Great Unknown One) (Angel Menendez), who is going to sell the stone to Dr. Igor (also Angel Menendez). Alicia is being forced to work for the Gran Desconocido because he is holding her father prisoner somewhere.
Santo arrives in Colombia and is met by Lt. Víctor Valle (Cesar del Campo) of the local police. Valle is suspicious of Lina (Mara Cruz), a blonde who became acquainted with Santo on the flight. As it develops, she is the courier who will take the emerald back to New York when it is delivered to Igor.
During a Santo wrestling match, a sniper attempts to shoot Santo. The assassin reports to Mario (Frank Brana) in a nearby nightclub, which also happens to be the hangout for Dr. Igor, his assistant, and Lina. Valle spots Lina talking to Igor, which confirms his suspicions about her.
The next day, Santo and Valle try to tail Lina and Igor through downtown Bogotá; they see Lina pass something (or get something) from Alicia. Alicia and her men flee to their hideout, with Valle and Santo in pursuit (Santo has to ride up the side of a mountain on top of an aerial cable car). After a short tussle, Alicia manages to escape.
Mario's henchman pays off Santo's next ring opponent, who tries to kill him during the match, but fails. The belly dancer in the nightclub is really X-25 (Johana Aloha), a police agent. She sends Santo a message to meet her in her dressing room. However, while Santo is chatting with Lina at a nearby table, the assassin--who just happens to be wearing clothes identical to those Santo is wearing, puts on a Santo mask in his pocket--murders X-25. Santo and the killer have a brief fight, but the fake Santo escapes.
Alicia wins a wrestling match and asks Mario to join her in her dressing room. Mario's girlfriend (Celia Roldan) finds them kissing, and in a jealous rage calls Dr. Igor and says Mario is going to double-cross his boss. She then tips off Santo that Igor will be leaving the city by private plane. Santo stows away in the plane and is taken to Igor's hideout, where Alicia's father has been forced to cut the giant emerald down to a smaller gem.
The Gran Desconocido reveals himself to be Dr. Igor. He has Mario tossed off a cliff for his alleged treachery. Mario's girlfriend is to be next, but the arrival of Santo and the police save her. Alicia is shot to death in a gun battle with the cops.
Santo has a sword fight with Igor's assistant, and the assistant winds up skewered. Igor and Lina flee in a light plane, with Santo and Valle in pursuit in a large Colombian army transport plane. Army paratroopers capture Igor's hideout.
Igor and Lina land their plane and escape by boat, headed for Brazil. Santo's plane is too big to land at the same strip, so he has to parachute out. A helicopter picks him up and drops him on Igor's boat. Igor--who is a rather elderly, thin man--unwisely tries to fight Santo and winds up in the river. Igor it is assumed is eaten by crocodiles.
Santo reports that Igor and Lina were drowned, so Lina can have a chance to go straight. However, she later steals the emerald from Santo and he has her stopped at the airport and arrested.