Zolok, a mad scientist, dreams of ruling the world from his underground city deep in Africa. He annouces his intentions by causing a worldwide series of electrical storms. Other technological marvels include a rejuvenation ray, a machine that makes giant zombies out of men and a death ray.

The entire world is plagued by incesant atmospheric storms. Bruce Gordon, an intrepid young electrical engineer using a "magnetic detector" that he has invented, traces the source of the disturbances to an unexplored region of central Africa. With the financial bacing of the government, Bruce travels there with his friend Jerry and two associates, Colton and Reynolds.

In Africa, Bruce meets Butterfield, a grizzled, unscrupulous trader, and with his magnetic detector learns that the violent storms emanate from nearby Magnetic Mountain. Within Magnetic mountain lies 'The Lost City', a super-scientific metropolis ruled by Zolok, a maniacal, strangely garbed technical wizard. Zolok's assistants include Gorzo, a malignant, hunchbacked dwarf, and Appolyn, an obedient muscle-bound henchman. It is Zolok who has caused the disasters plaguing mankind with the intention of conquereing the world, but Zolok's scientific marvels are really the creation of Dr. Manyus. Manyus, held captive by Zolok, is an elderly, benolent genius, forced to comply with zolok because Manys' beautiful daughter Natcha is also imprisioned by the madman.

Zolok tricks Bruce Gordon's expedition into entering the Lost City, forcing Natcha to scream over a loudspeaker as a lure. Within the bizarre futuristic city, Bruce and Jerry discover the extent of Zolok's ruthlessness when the learn that he commands an army of lobotomized African giants, created in his laboratory by physically transforming the local inhabitants.

Meeting zolok in his lair, Bruce is informed that he will either assist zolok or be transformed into a lobotomized zombie. Colton and Reynolds, also captured by Zolok, have managed to leave the Lost City with dr. Manys in a plot to steal his technological secrets and double-cross Bruce Gordon. Learning this, Natcha informs Bruce and Jerry, leading them out of the Lsot city and into the surrounding jungle in an effor to rescue her father.

Colton and Reynolds are eventually killed and the amoral Butterfield winds up forming an alliance with Bruce and his friends. After a harrowing series of misadventures involving Arab slave traders, marauding giant zombies, a tribe of pygmy 'spider-men' and a beautiful, love-starved jungle queen, Bruce, Jerry, Natcha and Dr. Manyus are recaptured and taken back to the Lost City, where an enraged Dr. Zolok tries to kill Bruce with a laser-like death ray. Aided by rebelling tribesmen, Butterfield invades the Lost City to rescue his newfound friends, and they escape.

Zolok, now totally insane and cackling wildly, attempts to destroy the entire world with his laboratory devices, but the powerful machines backfire and Zolok only succeeds in blowing up himself, the Lost city and most of Magnetic Mountain. With the threat to civilization ended, Bruce and Natcha, now ramnticaly involved, prepare to leave Africa and return home.