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.
When a rare species of butterfly is found in a mysterious valley in Japan, a pair of entomologists go to investigate and find more. They discover Varan, a giant monster, Who decided to leave the valley and head straight for Tokyo.
A war widow with a young boy manages a farm with her bossy mother-in-law. When a reporter comes to interview her, the two begin an affair. He turns out to be married and won't leave his wife. Her older brother tries to marry off his children and hang on to/ extend his farm through an advantageous marriage in the face of threatened land confiscation and the desire of his children to get comfortable urban jobs instead of the backbreaking work in the paddy fields under parental control.
Shows the devastation caused by the atomic bomb, and by use of a fictional storyline, portrays the struggle of the ordinary Japanese people in dealing with the aftermath.