Japanese miners are killed by giant prehistoric insects awakened by nuclear testing. After dealing with the bugs, the military discovers an even bigger threat has been awakened by the tests. Yup, it's Rodan, a pterodactyl-like monster that flies at super-sonic speeds. Soon another Rodan shows up and the two wreak havoc. What in the world will Japan do?
Set six months after the events of Gamera, the Giant Monster, a meteorite collides with the Z Plan rocket transporting the creature to Mars. Now free, Gamera returns to Earth and destroys Kurobe Dam in Japan. At the same time, three mercenaries are sent by Kano, a World War II veteran, to an island in the South Pacific to retrieve a huge opal he once found and hid in a cave. Despite warnings from the local villagers, the trio find and locate the opal, but one dies from a fatal scorpion sting. The second man, Keisuke, Kano's younger brother, is betrayed by his fellow expeditioner Onodera and apparently killed in a cave-in.
In the Arctic, an unknown aircraft is shot down by an American jet fighter. The aircraft crashes and its cargo, a low-level atomic bomb, explodes. The resulting cataclysm awakens a prehistoric monster that has the appearance of a giant turtle with teeth and large tusks. Japanese scientists on an expedition nearby (including Drs. Hidaka, Kyoko and Aoyagi) are given a "devil stone" by an Inuit chieftain, who explains that the creature is called Gamera.
When a rare species of butterfly is found in a mysterious valley in Japan, a pair of entomologists go to investigate and find more. However, when they get there they find an uncharted lake and as they are observing it they are caught in a landslide and killed. A reporter named Yuriko, the sister of one of the men decides to go to the area to find out what exactly happened. She is accompanied by another entomologist named Kenji and a reporter named Horiguchi. When they get to the village where the men were last seen alive they find out about a legend regarding a giant monster. They soon find out that it is not a legend and the monster named Varan is very much alive. Soon Varan leaves the valley where he has lived for millions of years and is heading for Tokyo.
In 1973, Gamera sacrifices his life to rid the world of the Gyaos once and for all. Thirty-three years later, a small boy, whose father witnessed the 1973 event, named Toru finds a mysterious egg. From it, hatches a small Turtle. Toru and his friends raise the turtle, who turns out to be a small Gamera. After a new man eating creature named Zedus, it's up to the small Gamera to save the world as the previous Gamera had done before.
