In Mexico City in 1661, Baron Vitelius of Estara is condemned by the Inquisition and sentenced to be burned at the stake. As this sentence is carried out, the Baron promises that he will return with the next passage of a comet, and slay the descendants of his accusers. Thus in Mexico City in 1961, the promised comet returns, carrying with it Baron Vitelius, who takes advantage of his considerable abilities as a sorcerer to carry out his threat: he is able to change at will into the hairy monster of the title in order to suck out the brains of his victims with a long forked tongue; furthermore, he has strong hypnotic capabilities and is able to render his enemies motionless or force them to act against their wills.
The Brainiac has received little attention from critics upon its release. Jon Condit from Dread Central gave the film a score of 4/5, writing, "Say what you will about the story and its title monster, El Baron Del Terror succeeds in capturing the look and feel of the classic black & white Universal monster movies of the Thirties and Forties that it was clearly influenced by. The whole film has the vibe of a horror film from that era, albeit a totally gonzo film from that era." Dave Sindelar, on his website Fantastic Movie Musings and Ramblings listed the film as his favorite Mexican horror film, also noting that the film was "supremely silly and can’t really be taken seriously". Kevin Nickelson from Classic Horror.com gave the film a positive review, writing "The Brainiac deserves some credit for having a good idea to begin with. Using gothic horror as a platform to tell a story of fanaticism and frigid sexual mores is an intriguing, if not original, concept. It’s just a shame that it gets sandwiched inside a creative and technical mess of a film. Still if you’re into badly dubbed and low budget cinema involving sorcerers, inquisitions, comets, sexually inhibited puritans, and astronomy," TV Guide awarded the film three out of five stars, calling it "competent and entertaining, despite the dreadful dubbing and cuts made under Murray's supervision". The reviewer also praised the film's expressionistic cinematography, and monster design. The Terror Trap called the film "hilarious fun thanks to its shameless ability to discard logic behind its pseudo sci fi plot" The film has developed a cult following since its cable-network TV appearance and is now considered a cult classic by younger generations.
