A westerner named Casey, studying Ninjutsu in Japan, is asked by the Sensei to return to New York to protect the legendary Yoroi Bitsu, an armored chest that contains the weapons of the last Koga Ninja.

A ship-wrecked man floats ashore on an island in the Pacific Ocean. The island is inhabited by a scientist, Dr. Moreau, who in an experiment has turned beasts into human beings.

The life of the greatest karate master of a generation.