In an effort to find an economic means of purifying salt water, a joint U.S.-Japanese military command is set up on an isolated Japanese island where an unusual salt water lake is situated. However, their purifying experiments arouse the prehistoric monster Obaki from hibernation at the lake's bottom, and it proceeds to attack Japan. Although made by a U.S. independent film company, this film was based on a Japanese Toho monster film of 1958, "Daikaiju Varan", from which all of the monster effects scenes and a few incidental dramatic shots were edited into it.

A widowed high-school teacher tries to raise his four children alone.

After learning that he has accidentally killed a man in a fight, Unokichi must look after the man's pregnant widow.

Japanese Navy air cadets train for the attacks on Pearl Harbor and the HMS Prince of Wales.