Volcanic activity frees giant scorpions from the earth who wreak havoc in the rural countryside and eventually threaten Mexico City.
Giant scorpions demolish Mexico City. They have been released from underground caverns by a series of volcanic eruptions, and it's up to Hank, an American geologist to stop them.—Marty McKee <[email protected]>
After unusually large volcanic eruptions and earthquakes disrupt the Mexican rural countryside, geologists Arturo Ramos and American Henry "Hank" Scott drive to the site of the volcano. At an abandoned gas station on the way they find a neglected baby and a strangely demolished police car. Nearby the geologists discover the body of the policeman, Sgt. Vega, who died with a horrified expression on his face after firing all the cartridges in his revolver. Although he is drained of all blood, no trace of blood is evident around his body. Taking the baby with them, the geologists continue to San Lorenzo, where they are welcomed by the village priest, Father Delgado, who is trying to comfort the distraught villagers. Delgado explains to them that several villagers mysteriously disappeared and their disfigured bodies were recently found. He continues that the mutilated corpses of steers frightened the vaqueros who work at a nearby ranch into abandoning their jobs, and rumors are spreading that the "demon bull," an ancient symbol of evil, has returned. The next day, the Mexican army arrives to investigate the mysterious deaths. Although advised by Maj. Cosio to postpone their investigation, Hank and Arturo resume their journey to the volcano. While looking through binoculars, Hank sees Teresa Alvarez, the owner of the ranch, fall off her horse. While Hank helps Teresa, Arturo explores the area and collects an interesting piece of obsidian. After driving Teresa to San Lorenzo, where she has business, the geologists meet with the toxicologist running the military's makeshift laboratory, who tells them that Vega died from poisonous venom and that large animal prints were found in the area. At Teresa's invitation, Hank and Arturo accompany her to her estate and meet Pio the foreman, Florentina the housekeeper and Juanito, her seven-and-a-half-year old son. After dinner, Arturo shares his discovery: A live scorpion is trapped in the piece of obsidian he collected. As telephone linemen contact Teresa to tell her phone service has been restored, the linemen are attacked and killed by gigantic scorpions. Hearing their screams over the phone and noting that the cattle and Juanito's dog Pancho are restless, Hank and Arturo investigate. After encountering the scorpions and discovering that guns provide no protection, they take Teresa, Florentina and Juanito to San Lorenzo. Upon arriving in the village, Hank and Arturo are introduced to Dr. Velazco, a specialist from Mexico City. Velazco identifies Arturo's scorpion and the giant ones as Triassic Era survivors that were living underground. He believes they were spewed out by the volcanoes from the bowels of the earth. Knowing that bullets and traditional weapons do not affect the creatures, Velazco suggests locating the creatures' nest, which will probably be found in a newly-formed chasm, and flooding it with poisonous gas during the day while the scorpions are inactive. Velazco, Hank and Arturo volunteer to assist the military and Teresa offers her services as guide. The next day, the team searches and finds an opening that leads underground, which appears to be the creatures' point of exit. When the scout, Mendoza, accidentally falls into the chasm, Arturo and Hank volunteer to be lowered in a cage to the bottom. From below, they report by radio that the cave is too large to gas successfully and that Mendoza died from the fall. Inside the caverns, Hank and Arturo watch as a giant scorpion fights a thirty-foot-long worm, and then other scorpions that are lured by the blood. The scorpions fight among themselves, until a "granddaddy" scorpion kills his competitors by biting them under the throat. When Hank and Arturo hear the screams of Juanito, who has "stowed away" with them and hidden in the cage, they follow the sound to its source and find that Juanito is being chased by a young scorpion. After they rescue the boy, another scorpion snaps their cage from its rope. Arturo grabs the end of the rope as it is lifted out of the chasm, and rides it to the surface. From there, he arranges for Hank and Juanito to be rescued. The group then makes new plans: Because gassing the nests is not feasible, they instead dynamite the opening to trap the creatures inside. After assessing that the explosion sealed the opening, the group disperses and resumes their normal lives. However, soon after, Arturo and Hank are called to Mexico City by Velazco, where they meet with civilian defense officials and Army officers, who have discovered from aerial photos that several scorpions are loose and heading toward Mexico City. To avoid widespread panic, they decide to withhold this information from the public. When asked for advice about defeating the creatures, Hank and Arturo report that the scorpions' throats appear to be vulnerable. A strategy meeting is then scheduled for Friday, and during the next few days, Hank and Teresa get to know each other better and grow closer. Meanwhile, the scorpions close in on the city and attack a train, killing many on board. After ravaging the train and its riders, the creatures attack each other in a blood lust. Only one survives, and it single-mindedly continues toward the city, killing anyone in its path. The city is placed under martial law and a meat truck is used to lure the creature into the stadium, where armored trucks and artillery surround it. Although the creature is shot at by a variety of weapons, none are effective. As a last resort, Velazco has devised a weapon fashioned from a large harpoon attached to a copper wire that will conduct electricity. Although the first shot misses and the gunner is accidentally electrocuted, Hank takes over and fires a second time. The projectile lodges in the scorpion's throat and, via the copper wires, the creature is electrocuted.
The movie opens with an exploding volcano in Mexico. A narrator describes the latest volcanic eruption. Title and Credits follow. A Jeep with a trailer is being driven over the volcanic debris by an American Geologist, Dr. Hank Scott (Richard Denning). He is accompanied by Dr. Arturo Ramos (Carlos Rivas) a Mexican Geologist. The area is still smoldering. They encounter a telephone crew working to restore phone service. They ask directions to San Lorenzo and if anyone has made it through. They are told a police car went through earlier and hasn't returned. Arturo and Hank stop driving when they hear a strange roar. The Jeep needs water and they see a farm house ahead. They call out for anyone home at the farm house. Arturo looks for a well and some water for the Jeep as Hank goes into the house calling out. Arturo calls Hank back outside after he finds a damaged and abandoned police car. The police radio calls for Sgt. Vega, but he is nowhere to be found. Hank starts to call on the radio, but thinks Arturo should do the talking. He hands him the microphone to explain the wreckage to the dispatcher. They hear what sounds like a rattlesnake in the house. They go in to investigate and find a baby still alive. The house is a shambles. Hank carries the baby boy back to the Jeep. They find the dead policeman amid the wreckage outside. They report that and drive to San Lorenzo.
They arrive in San Lorenzo amid a crush of terrified peasants. The local Priest, Father Delgado (Pedro Galvan), comes to greet the two scientists. Hank gives the baby to the priest. A local woman identifies him as Manuel Tiburcio. His parents are missing and presumed dead. She takes the baby. Father Delgado explains, over a meal, that the deaths began the first Sunday after the eruption of the volcano. Hank asks about the superstition of the huge "demon bull." Delgado explains that, "The demon bull is a symbol of evil among many ancient civilizations." All the men of the Miraflores Ranch abandoned the place two days ago. They brought the demon bull story with them. Hank and Arturo spend the night then leave the next morning. Major Cosio (Arturo Martinez) asks Hank and Arturo not to being their expedition. They set off on their journey, but tell Cosio they intend to return to San Lorenzo that evening. Once on the road, they stop to get their bearings and plan their approach. Hank spots a woman on a white horse. He gives Arturo the binoculars to look, but by the time he gets them in focus the rider has fallen off. All he sees is a horse, which surprises Hank because he saw a rider. And a beautiful woman at that. They drive off to find her. Teresa Alvarez (Mara Corday) is all right, just a little embarrassed. She is the owner of the Miraflores Ranch and has been thrown by her horse, Lucero, before. She tells the two scientists that Lucero will find his way back to the ranch on his own. Arturo goes to retrieve her saddle and sees a piece of obsidian. Teresa asks for a ride to San Lorenzo. She needs ranch hands to help with her cattle. She also confirms the two geologists will make Miraflores their base camp. When she arrives in San Lorenzo she talks her ranch hands into returning to the ranch. As Arturo and Hank enter the church, they are summoned to see the Major and Dr. de la Cruz (Pascual Pena). They are witness to the policeman's autopsy. De la Cruz suspects an organic poison but he is unable to identify the exact one with his primitive field lab.
Arturo, Hank, and Teresa drive to Miraflores. Her ranch hands follow on horseback. She invites them into the house. Arturo comments, "Not only comfortable, but cool too." She calls to her housekeeper Florentina (Fanny Schiller) and Juanito (Mario Navarro) to assist her guests in getting settled. Hank and Teresa engage in small talk. It is obvious Hank is romantically interested in his hostess. Arturo calls them over to examine the rock they picked up earlier. Inside the obsidian is a trapped scorpion. When Arturo breaks it open a live scorpion escapes. Hank puts it in a jar. Before Hank and Teresa can go outside, the telephone rings. She excuses herself to answer it. The lineman explains her phone line was the last to be fixed and he is testing the line. A man on the ground turns around and is confronted by a huge scorpion that roars and drools. It grabs the man and carries him under a bridge into a dry river basin, or arroyo. The man still on the pole notices the commotion and calls to his colleague, Gaetano. Gaetano gets in the phone truck, but the scorpion flips it over killing the man. He chases the lineman back up the pole, picks him off, and kills him. Arturo, Hank, and Teresa run to the arroyo bridge. The dog, Pancho, runs off. Juanito chases after the dog, and sees the giant scorpion. He flees in another direction as Hank, Arturo and some ranch hands fire their rifles at the creature.
Another volcanic eruption damages the church. Refugees scatter as a giant scorpion attacks. The cattle stampede and the occupants of Miraflores Ranchero evacuate to the city of San Lorenzo. They encounter Dr. Velazco (Carlos Muzquiz) who just arrived amid the commotion. Dr. Velazco tells them he was sent to be in charge of emergency arrangements. San Lorenzo is to be evacuated. Velazco identified the poison as scorpion venom. He proposes poison gas as a weapon against this newly discovered species--Scorpionida Rex.
The ranch hands, and the army search for the lair of the scorpions. Hank, Arturo, Teresa, and Dr. Velazco drive along and spot dead cattle. A man on a horse finds the opening around the volcano, but falls in off his horse. Hank and Arturo decide to go down into the crevasse. When they go to their trailer to get some climbing equipment they discover a stowaway, Juanito. Hank and Arturo dress in protective clothes; Hank has a camera. Hank and Teresa kiss. The two geologists get into a metal cage and are lowered down into the cave. Midway down they discover a large scorpion on a ledge. Hank takes its picture and they continue their descent. At the bottom they find themselves in a huge cavern. They exit the cage and begin to explore. They are unaware that Juanito has joined them on their exploration of the cavern. They spot and photograph a huge inchworm and find the remains of the man who fell in, Mendoza. A nest full of scorpions approaches. Juanito exits the cage to look around on his own. A scorpion attacks the giant inchworm. Then a larger scorpion attacks a smaller one, killing it with its stinger. Juanito pulls at a trap door and is chased by a giant tick. He hides in a cave as Hank and Arturo dispatch it with their rifles. The three run back to the safety of the cage, but the scorpion arrives first and destroys it. They watch helplessly as the creature snaps the cage from the line. Arturo hangs on to the line as it is pulled up. He is safe on the surface. They make a loop on the cable and send it down for Hank and Juanito. They are pulled to the surface. Velazco orders the opening closed with explosives.
Velazco is back in Mexico City. He calls Hank in San Lorenzo and orders him and Arturo to Mexico City for their report. Velazco arranges an airplane with room for three. Hank wants Teresa along. The three arrive in Mexico City and are met by Victor Esteban. He takes them to the University to meet with Dr. Velazco. Hank asks for an explanation. Recent photographs of the San Lorenzo area showed renewed activity. There is an underground system of caves and caverns that might be used by the scorpions. One arm of the system is twenty miles from Mexico City.
Hank and Teresa go to a night club for a drink. They discuss dinner plans. They have dinner while a train from Monterrey to Mexico City is attacked by the scorpions and derailed. A swarm of them attack and kill the passengers. A larger one, the Black Scorpion, arrives and kills some of the smaller ones. Hank and Teresa hear the report on the radio in their rented car after dinner. The Black Scorpion is headed for Mexico City. The city is ordered evacuated. The military enters the city as does the giant arachnid. The plan is to lure the scorpion into an arena then shoot it with a projectile attached to an insulated wire then electrocute the beast with 600,000 volts. They bait the arena center with tons of steer carcasses. When the scorpion arrives it crawls over the stands and on to the floor of the stadium. Tanks and helicopters attack the creature. The first shot of the projectile misses, but the power was applied anyway. A soldier retrieves the projectile and is electrocuted. Hank and Arturo reload the gun with the projectile. Meanwhile the scorpion is making short work out of the tanks and helicopter firing on it. The second shot hits its mark. The power is applied and the scorpion dies. Hank and Teresa depart the arena, arm in arm. The rest stare at the dead scorpion. We close with a zoom out to a long shot of the dead scorpion.
