Mesa of Lost Women

Tarantella, one of Dr. Aranya's spider-women, kills Doc Tucker as part of her predatory nature. The opening scene establishes her as a deadly, seductive creature who uses her spider-like claws and hypnotic charm to lure and murder men. This attack serves as a prologue that sets up the movie's central horror: Aranya's experiments have created women who function as deadly predators.

When Leland Masterson denounces Aranya's spider-human experiments as evil and blasphemous, Tarantella punishes him by injecting him with a drug that renders him simple-minded. This turns Masterson into a compliant puppet controlled by Aranya, eliminating his threat as a dissident scientist who could expose or stop the project.

After shooting Tarantella, Masterson believes she is still a danger to everyone around him. He takes Jan van Croft, Doreen, and George hostage to force them onto Jan's aircraft, using them as leverage to reach Zarpa Mesa where he intends to confront and stop Aranya's experiments. His mind is still impaired from the drug, making him erratic and desperate.

Wu is secretly working with Masterson and sabotages the airplane to ensure the group crash-lands on Zarpa Mesa, allowing Masterson to return to Dr. Aranya's laboratory. Wu's betrayal is discovered mid-flight, but he is killed by the spider-women before he can fully explain his motives or escape.

Tarantella possesses regenerative abilities, one of the key results of Dr. Aranya's growth hormone experiments. When Masterson shoots her at the border bar, she appears to die but quickly regenerates from the wound and escapes into the night, ready to continue hunting victims.

After the survivors are captured by Aranya's spider-women on Zarpa Mesa, Aranya restores Masterson's intellect because he needs Masterson's scientific expertise for his experiments. With his mind returned, Masterson pretends to cooperate while secretly planning to destroy the laboratory and stop the project.

With Masterson's mind restored, he helps devise an explosive plan to destroy the laboratory. While Grant and Doreen restrain Aranya and Tarantella, Masterson sets the explosives. The trio escapes as the laboratory burns, though Masterson sacrifices himself in the blaze to ensure the monsters are destroyed.

The ending reveals that Dolores Fuller, one of Aranya's spider-women, survived the laboratory explosion. This creates an ambiguous, unsettling conclusion, while the main threat seems destroyed, the survival of at least one spider-woman means the horror and danger from Aranya's experiments could continue.

The narrator interrupts Grant's account multiple times to shift focus toward Pepe, hinting at truths the American characters refuse to accept while the Mexican characters already know. This narrative technique suggests Pepe may have prior knowledge of or connection to the events on Zarpa Mesa, adding mystery to his character.

George, the asylum nurse who came to collect Masterson, is killed while exploring the harsh desert terrain of Zarpa Mesa. His death occurs early in the survivors' ordeal on the mesa, reducing their group and removing the only person who knew about Masterson's past.

After crash-landing on Zarpa Mesa and experiencing trauma, including George's death and Jan's mental breakdown, Grant and Doreen lean on each other for comfort and courage. Their bond strengthens as they face the dangers of the mesa together, eventually leading them to work as a team to escape the laboratory.