On Sergio Island in 1970, the body of the sea monster Gezora was taken over by a rouge alien virus, known only as Yog. The alien virus within the cuttlefish caused him to grow to gigantic size and then sent Gezora to attack the natives of the island where Yog’s spacecraft crashed. The giant cephlapod terrorized the island for some time, but was finally driven away when the islanders and Japanese who came there fought back against Gezora with the monster’s weakness, fire. Severely injured by the attack, Gezora retreated into the ocean and sank beneath the waves. The Yog entity, realizing this body was dying, abandoned Gezora before seeking out a new host body. This didn’t take long, for soon Yog found a stone crab and mutated it into the monster Ganimes, directing the giant crab back to Selga Island to destroy the humans that had defeated him before, but Ganimes was quickly destroyed when it was lured into a pit lined with explosives and blown apart. However, once again the Yog entity was not harmed and it split to possess three creatures, a Japanese industrial spy on the island, a rock turtle, and another stone crab. The crab transformed into another Ganimes while the turtle became Kamoebas, both monster being directed to attack the islanders once again. All looked lost for the islanders for a while, but the industrial spy was actually able to throw off the possession of Yog for a brief time and released the island's bats, their high-pitched sonic shreiks hurting Yog and forcing Kamoebas and Ganimes back. The bat's sonic squeaks also interrupted Yog’s control over the monsters and Ganimes and Kamoebas attacked one another. The battle soon moved to the island's volcano, where Ganimes was able to throw Kamoebas in, but not before the giant turtle succeeded in biting into one of Ganimes' pincers, dragging him into the volcano as well. The heat of the molten lava killing both monsters and the Yog entity as well, ending the virus' reign of terror forever.