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.

Men are being murdered by a psycho called "The Telegian," who uses a matter-transmitting device to locate his victims.

An Ishiro Honda film.

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 decides to leave the valley and head straight for Tokyo.

Nuclear tests create a radioactive man who can turn people into slime.

In Japan, scientifically advanced invaders from the war-destroyed planet Mysteroid cause an entire village to vanish, then send a giant robot out to storm the city by night, after which they request a small patch of land on Earth and the right to marry earthling women, claiming to be pacifists. Mankind must decide whether to capitulate or to resist.

Mining engineer Shigeru investigates the disappearance and death of his fellow coworkers when prehistoric nymphs are discovered emerging from the mines. After an attack on the local village, Shigeru heads deeper into the mines only to make a more horrifying discovery in the form a prehistoric flying creature. Soon a second monster appears as the two converge in Fukuoka.