Having taken care of Frankenstein's Daughter already in a previous film, Dr. Frankenstein must now be dealt with. Dr. Irving Frankenstein, that is.
After a snappy title sequence with a swingin' and funky soundtrack we're shown a city where beautiful women are vanishing and returning as zombies to murder their friends and family in their homes. It's clear to authorities that this is the work of Dr. Frankenstein, and true enough, it's the good doctor's attempt to garner fear and respect, which clashes quite a bit with his want and need to live in secret and conduct his dubious research. He is of course attempting to unlock the mysteries of immortality, and thus far, his greatest Frankensteinian work is in Golem, a tall and ripped black man immune to bullets and to the screams of his victims. He's powerful, but he's slow and not very bright (such a racially sensitive film!), and Frankenstein surmises that to create the ultimate reanimated warrior he will need the superior brain of El Santo. Both Santo and Blue Demon aren't quite going to give him what he wants. Interestingly, Blue Demon actually has to come to Santo's rescue at one point, finally proving to be more than just El Santo's sidekick. He seems much more like his own entity in this film, whereas before he was more like an extension of Santo's good will.
Of the Santo films I've seen, this one has the most action, as it seems to be chock full of car chases, gun play, and thugs in dark warehouses and on dark streets just asking for a pounding. In addition, as always, we're given awesome introductory wrestling matches between Santo and Blue Demon and their various lucha libre opponents. Which reminds me: something I really like about this Santo installment is that more than any of the others I've watched, you're reminded the most frequently that Santo and Blue Demon are professional wrestlers, and have wrestling careers to maintain when they're not tangling with the evil forces of Mexico. The plot actually ends off at a wrestling auditorium with a wrestling match between the disguised and remote-controlled Golem and Santo and Blue Demon in the fucking ring. Way cool.