Dr Alexander Thorkel (Albert Dekker) has isolated himself from the scientific mainstream - literally, as he now carries out his experiments in his laboratory deep in the Amazon Jungle. There is a mine nearby that he draws radioactive material from, but what exactly is he planning? His assistant, Dr Mendoza (Paul Fix) sees what Thorkel is up to and in the lab one day he confronts him: he's messing with the forces of nature and must cease his work immediately. However, Thorkel doesn't take kindly to this interference and takes drastic action, striking Mendoza and smashing his head into a radioactive machine, killing him. But Thorkel's eyesight is failing and he needs another pair of eyes to assist him, so he sends for a group of scientists from America... and they're foolish enough to accept his offer.
If there's any science fiction film that looks like the cover of Weird Tales magazine come to life, it's Dr Cyclops, which was based on a short story by Tom Kilpatrick, and adapted by him to the screen. In its title character, the film features one of the archetypal mad scientists, and of course his schemes make no real sense as what he wishes to do, and succeeds in doing, is shrinking animals. We never find out the precise reason for this except that it will look cool and provide fantastical thrills for the story, and that's all you need really, as the special effects for the time, hey, even for modern times, are excellent and a lot of fun.
But first the victims, sorry, scientists have to make their way to the jungle, and they are led by Professor Bulfinch (Charles Halton), with Beautiful Lady Scientist - already a staple of the genre - Mary (Janice Logan) and the more rugged Bill (Thomas Coley) as his assistants. Along the way they pick up the man who owns the mules, Steve (Victor Kilian), who inexplicably wants to tag along, so when they reach the encampment there are four of them, all ready to be subjected to Thorkel's radioactive rays. They have a chance to get away, as all they were needed for was to confirm some results for the Doctor, but their interest is piqued and they decide to hang around. But why is Thorkel's servant Pedro (Frank Yaconelli) searching for his horse? What could have happened to it?
I'll give you three guesses. That's right, Thorkel has shrunk it, and soon, annoyed at the way the party don't take the hint and leave, he tricks them into his lab to examine his apparatus (oo-er), whereupon he locks them into the shrinking chamber and pulls the levers. He now has a selection of tiny humans to play with, and the unfortunates do their best to escape from his clutches, only to find the jungle holds many perils for the miniscule. As their height diminishes, so do their personalities and at initially they are little better than two-legged mice scurrying around, yet as they discover ways to fight back, they regain their humanity. Through a selection of oversize props, forced perspectives and back projection, the nightmare world is ingeniously realised, and the little people have brushes with a pet cat (called Satana!) and an alligator among others. Disappointingly, none of them are eaten by wild animals, as the ones who die do so at the hands of the megalomaniac Thorkel (Dekker is ideally cast) who regards his subjects as his to kill as he pleases now they are physically diminished. Music by Gerard Carbonara, Albert Hay Malotte and Ernst Toch.