A reporter stumbles upon weather experiments on a tropical island, discovering giant mantises, a castaway woman, and an infant monster that Godzilla must adopt as his own.
A plane spots Godzilla heading off to an island in the South Seas named Sollgel, with the monster seemingly being called there. Reporter Goro Maki soon stumbles on Sollgel and finds scientists conducting weather experiments to feed a growing global population. He soon discovers that the experiments have mutated mantises in giants named Kamacuras. As Maki explores the island, he finds a cast away woman named Saeko as the weather experiments inadvertently cause the mantises to grow even bigger. The mantises soon uncover a giant egg which contains a defenseless infant that is rescued by Godzilla. Maki and Saeko soon observe Godzilla adopt the infant as the monster learns to care for the child and raise it as one of his own.—Brian Washington <[email protected]>
A plane is caught in a storm when the crew spots Godzilla heading towards the remote Island of Sollgel. Something is calling out to the monster. On Sollgel, a team of United Nations scientists led by Dr. Kusumi is conducting weather controlling experiments to grow food in unsuitable climates and help resolve world hunger. They notice radio interference and spot a plane that drops a man via parachute. Researchers Kusumi and Morioa meet the man who introduces himself as Goro Maki, a freelance reporter. Initially, the scientists refuse to allow Goro to stay but they eventually capitulate and allow Maki to stay to help cook and clean. As Maki is accepted, a giant mantis is seen moving through the jungle.
Maki attempts to get a story from the scientists, only to notice the bad mood of Furukawa. Maki then heads out into the jungle to collect parsley for food and explore the island. He sees a beautiful native girl swimming in the waters of the island before she gets startled and disappears. That night, Maki discusses with the scientist's about their experiment and brings up the girl he spotted. Kusumi states the island is uninhabited as Furukawa mentions how he wants to get the experiments over with so they can leave. Later on, the weather control experiment is ready to commence as Maki attempts to locate the native girl before the area freezes. Maki is unable to find her as the experiment fails and results in a scorching heat wave, accompanied with severe storms. After several weeks, the storms cease and Kusumi and Maki wander across the island. They spot several mantises that have mutated in giants due to the experiments. Maki names them "Kamacuras" as a group of them approach a dirt mound and revealing a huge egg. The Kamacuras smash the egg with their claws until it breaks and a helpless monster, that Maki identifies as a baby Godzilla, crawls out.
At the scientists' base, Furukawa is succumbing to cabin fever and attempts to leave the island. But Godzilla arrives and makes his through the base and jungle towards the Kamacuras to defend the helpless infant. The monster manages to kill two of the Kamacuras as a third one flies away. Having saving the child, Godzilla leaves as the native girl approaches to feed the baby some fruit. However, she is forced to flee as Godzilla has a change of heart and returns, allowing the infant to ride on his tail. Maki meets the girl and introduces her to the scientists as Saeko Matsumiya, a castaway along with her archaeologist father who died seven years prior. The group is then attacked by a Kamacuras as they decide to go settle in Saeko's cave.
Godzilla's adoptive son, Minilla, is revealed to have grown as he spends time near a lake with his father. He attempts to play with his father's tail but Godzilla gives a disapproving look and goes back to sleep. Maki and Saeko spends some time exploring the island, where Maki promises to take her to the mainland. Maki is then startled by a wandering Minilla but Saeko tells him not to worry. She feeds the monster more fruit before she and Maki are chased off as Godzilla arrives and reprimands his child. The child then throws a tantrum as a frustrated Godzilla frustrated drags him away by his tail.
The scientists study the notes of Saeko's father and notice the name Kumonga. They also realize that many of them are developing an intense fever. Saeko mentions that the red water from a nearby lake can be used to cure them and reveals that Kumonga is a giant spider that's been dormant on the island. She heads off with Maki to collect some water and spots Godzilla with his son, Minilla. Godzilla is attempting to teach his child to use his atomic breath, the monster's strict attitude being compared to Japanese parents by Maki. Frustrated, Godzilla then steps on the Minilla's tail causing a successful atomic blast. Maki and Saeko return with the water as Furukawa suffers a breakdown and accidentally shoots Kusumi.
Later on Saeko heads into the jungle to fetch some herbs for Kusumi when she has a run in with the Kamacurus. Minilla arrives and unsuccessfully attempts to drive the giant mantises away. The confrontation disturbs the sleeping Kumonga as Maki arrives to rescue Saeko. Godzilla also arrives to help his son against the Kamacurus. Kumonga then awakens an nearly traps Maki and Saeko as the pair escape back to the cave. But Kumonga arrives near the cave and traps everybody inside with it's webbing. Sakeo and Maki attempt to find another way out as Kumonga tries to attack them. Kusumi and scientists decide to freeze the island so they can escape. Above them, Minilla is facing off against Kumunga but is caught in the spider's webbing. The scientists make the preparations to enact their plan while Godzilla arrives to rescue Minilla. Godzilla faces off against Kumonga as the scientists succeed in dropping the temperature and start to freeze the island. They get out as an intense snowstorm begins while Godzilla and Minilla successfully manage to work together and defeat Kumonga.
Maki, Saeko, and the scientists leave on an inflatable boat as they observe Godzilla attempting to flee from the island. However, Minilla is unable to make it through the snowstorm and calls out to his father. Instead of saving himself, Godzilla heads back to comfort his son. Maki and the others are rescued as they observe the monsters from afar, father and son embrace each other as they settling in for hibernation.
