A team of United Nations scientists set up a research base on Solgell Island in order to test a weather-controlling device, which they hoped would allow them to alter climates around Earth to allow for the growing of food, potentially solving world hunger. The scientists produced the Radioactivity Sonde and Weather Control Capsule, and decided to test them on the island. However, something went wrong and the Radioactivity Sonde exploded, releasing huge levels of radiation onto the island. The radiation produced extreme heat waves and violent storms, and also mutated native Giant Praying Mantises into kaiju called Kamacuras. The Kamacuras discovered an egg on the island and broke it open, revealing Minilla, a baby Godzilla. Minilla's cries of distress attracted Godzilla himself to the island, who killed two of the Kamacuras and saved Minilla. Godzilla began raising Minilla as his son, and lived with him in the heart of the island, next to a hot spring of red water. While wandering on the island, Minilla accidentally knocked a rock into a gorge, awakening Kumonga, a giant spider. Kumonga attempted to kill the humans on the island, but they escaped to a cave where Kumonga could not reach them. Kumonga later trapped the surviving Kamacuras and Minilla in its web, and killed the Kamacuras. Before Kumonga could do the same to Minilla, Godzilla arrived and did battle with Kumonga. The humans repaired the Radioactivity Sonde and Weather Control Capsule in attempt to cool the island's climate and send the monsters into hibernation. While Godzilla and Kumonga battled, the devices were activated and it began to snow on the island. Godzilla and Minilla defeated Kumonga, and Godzilla attempted to escape the island before it froze over. Minilla fell down in the snow and cried out, prompting Godzilla to turn back and embrace him. The two monsters then fell into hibernation together while the island froze over. The humans were then rescued by a United Nations submarine. After the ice thawed away, the humans built a research station on the island, renaming it "Monster Island."