El Santo (above) and Capulina (below)
in characteristic settings
Meanwhile, we learn that the thefts are part of a larger plan by some old enemy of Santo's to lure the luchador into a death trap. The mastermind is assisted by a scientist and his pretty daughter, who disguises herself as a reporter in hopes of getting Santo to unmask. The scientist, we learn later still, is working reluctantly for his daughter's sake, while the daughter has somehow been convinced that Santo is some sort of murderer. The scientist's specialty is the making of robot duplicates who take the places of kidnapped men -- eventually including Capulina. The robot-vs.-wrestler fight justifies the title and looks more plausible than you'd first assume, once you see that Capulina is actually bigger than Santo. Eventually, though, the real Capulina escapes his captors but must pretend that he's his own robot duplicate or, as he understands it, a "rubber man." As well, the scientist's daughter realizes the error of her ways and helps our heroes defeat the mastermind. Good inevitably prevails.
By American standards, there's not much humor here beyond the inherent absurdity of the cinematic El Santo concept. He gets an understatedly weird solo moment set at his presumably impressive home, where he interrupts his breakfast to dump his secretary/mistress (?) into his pool, her explosion revealing her as one of the villains' robots. It's too bad such genius can't be used for humanity's betterment, Santo muses. That bit amused me more than all of Capulina's antics, but the comic's amiable idiocy sort of made me understand his popularity, which endured to the end of the 20th century. There's an audience for such bumblers in most places, but comedy, especially in the sound era, doesn't travel as well as fighting men in masks. Genre film buffs around the world know El Santo, I expect, but fewer know Capulina. Both are Mexican cultural icons, but Capulina seems more exclusively Mexican -- and they can have him.