Boris Karloff, Maris Wrixon, Gene O'Donnell, Dorothy Vaughan, Henry Hall, Selmer Jackson, Gertrude Hoffmann, Jessie Arnold, Billy Bletcher, Harry C. Bradley, George Cleveland, Ray Corrigan, Pauline Drake, Mary Field, Gibson Gowland
Dr. Bernard Adrian is a kindly scientist who seeks to cure a young woman's polio. He needs human spinal fluid to complete the formula for his experimental serum. Meanwhile, a vicious circus ape has broken out of its cage, and is terrorizing the townspeople. Can there be a connection?