THE BLACK SCORPION

An earthquake strikes Mexico, resulting in the overnight birth of a new volcano. Geologists Dr. Hank Scott and Dr. Arturo Ramos are dispatched to study this crisis at the village of San Lorenzo, the two men finding a destroyed house and a totaled police car en route. They find a dead policeman nearby, and an abandoned and seemingly orphaned infant. They take the infant to San Lorenzo and give it to friends of the child's missing parents, while being welcomed by the village's priest, Father Delgado. Delgado reveals that the property damage is caused by something that is slaughtering the livestock, the villagers believing the culprit to be a demon bull and have been pestering Delgado for divine assistance.

Undaunted, Hank and Arturo begin their geological survey as members of the Mexican army under Major Cosio arrive in San Lorenzo to begin disaster-relief efforts. Hank meets and falls in love with local rancher Teresa Alvarez, and makes friends with a young boy named Juanito. When the volcano erupts again, the culprits behind the disappearances and deaths are revealed as giant prehistoric scorpions. After killing a crew of telephone repairmen, the scorpions attack San Lorenzo with the Mexican military unable to harm them. The next morning, the scorpions have returned to their underground lair, leaving the authorities to seek the help of renowned entomologist Dr. Velasco. Velasco sends Hank and Arturo to scout the cavern to determine whether poison gas would be an effective means of extermination. While also fending off giant worms and spiders, Hank and Arturo observe that the scorpions kill each other by striking a small white spot on their throats. Returning to the surface, they report that the cavern is too vast for poison gas to fill it at sufficient density, so Velasco says their only choice is to seal the entrance with dynamite. Hank objects that there may be other entrances, but Velasco points out that all the sightings of giant scorpions have been traced to this source.

The giant scorpions resurface days later to attack a train. Some of the passengers are killed. In-fighting among the scorpions resolves with the largest of them killing the others before heading for Mexico City. Hank and Arturo come up with a plan to lure it to a stadium with a truckload of meat, with the military distracting it long enough to kill it by shooting an electric cable attached to a spear into the white spot on its throat. However, the spear misses. The soldiers neglect to shut off the power after the miss, so the gunman is fatally electrocuted when he attempts to reload the spear. Hank re-fires the spear himself, finally slaying the last scorpion.

The last giant scorpion is lured to a stadium and killed by electrocuting its vulnerable throat spot after previous attempts fail, averting further disaster for Mexico City.

The film concludes with science and ingenuity triumphing over a seemingly unstoppable force of nature. By exploiting the scorpion’s unique weakness, the protagonists underscore humanity’s ability to adapt and survive even when prehistoric nightmares crawl up from the depths. It's a signature creature-feature ending: the monster is vanquished, the city is saved, and the scientific method gets the last word.