A wild half-man, half-ape emerges from his countryside cave. People call him Trog, short for a prehistoric cave dweller called a troglodyte. To anthropologist Dr. Brockton, he's the scientific discovery of the age. To others, he's walking death. A grocer is impaled on a meat hook, a car is tossed aside like a twig, a child is kidnapped-- all after local resident Sam Murdock prods the brute into a blind rampage.