A wild half-man, half-ape emerges from his countryside cave and makes the news. People call him Trog, short for a prehistoric cave dweller called a troglodyte. For anthropologist Dr. Brockton, he's the scientific discovery of the age. To others, he's a creature on a murderous rampage after local resident Sam Murdock prods the brute. Who is the actual savage, "civilized" man or Trog?