When scientists exploring the Amazon River stumble on a “missing link” connecting humans and fish, they plan to capture it for later study. But the Creature has plans of his own, and has set his sights on the lead scientist's beautiful fiancée, Kay.
A dangerous combination of radiation and insecticide causes the unfortunate Scott Carey to shrink, slowly but surely, until he is only a few inches tall. His home becomes a wilderness where he must survive everything from spiders living in the cellar to his beloved cat.
A rogue scientist near a small desert town arouses the suspicion of the town's doctor when his lab assistant is found dead from a case of acromegaly, which took only four days to develop. As the doctor investigates, aided by the scientist's new female assistant, they discover that something is devouring local cattle and humans in increasingly large quantities.
