To assist with his work due to his failing eyesight, renowned biologist Dr. Alexander Thorkel (Albert Dekker) invites two prominent scientists and a mineralogist to his hidden Amazon jungle laboratory. Thorkel remains evasive about the nature of his experiments, and after the team evaluates his bacteria slides, he orders them away. When they refuse, Thorkel and his servant trick them into a chamber where Thorkel shrinks them down to microscopic size, and they escape to the terrifying jungle.