A U.N. science team is preparing for a super secret weather experiment on Sollgel Island in the South Pacific, and are experiencing strange readings on their instruments. Reporter Goru Maki surprises the team when he parachutes into the secret outpost. A preying mantis, roughly the size of a tall man encroaches on the research station, but is scared away by gunfire.
The next day, the scientists put their experiment into action. During the countdown, Maki rushes off to look for a mysterious woman he saw the day before. Due to outside interference with their equipment, the experiment goes horribly wrong and creates a terrible hot and radioactive storm, that lets up four days later.
As Maki and Kusumi survey the island for damage, they are surprised by giant preying mantis, who has grown to 160 feet long as a result of the radiation. They rush to one of the weather stations, and find three “Gimantis” unearthing a giant egg.
The next day, the Gimantis are successful at breaking open the egg, and a “baby Godzilla,” some 20 feet tall, rolls out, only to be attacked by the other beasts. Godzilla arrives onshore and wrecks the research station. The radio interference experienced earlier was apparently caused by the cries of the infant, known as Minilla. Godzilla battles the Gimantis, burning one with his nuclear breath as it attempts to escape. One hits Minilla in the face with a boulder, enraging The King of the Monsters. He pounds it into the ground and burns it. The third flies off to fight another day. Godzilla walks off, leaving Minilla behind, trying to crawl. The woman, who has watched all this, pulls a giant fruit from a tree and calls to Minilla. The small monster manages to get to his feet and accepts the fruit. Godzilla returns and offers his tail to Minilla, who hops on and rides as Godzilla walks off again.
The woman finds Maki in a nearby cave. Riko Matsumiya agrees to return to the now smashed research station. It turns out, she is the daughter of an archeologist who had died while on the island. Her mother died in childbirth. The scientists move their research station to her cave.
Minilla is kicking around boulders while Godzilla naps, with his tail swishing back and forth in his sleep. Minilla uses the tail as a jumprope, but accidentally jumps on it, waking Godzilla. He apparently admonishes Minilla, who wanders off and finds Riko and Mako frolicking on the beach. Godzilla wakes from his nap and finds Minilla at the beach. The baby throws a tantrum and throws himself on the ground. Godzilla pulls the baby by the tail and drags him back
At the cave, several of the scientists come down with a high fever. Riko says they can be cured of the mysterious illness by drinking Red Water, but must pass Godzilla and walk through Spiga’s Valley. However, Spiga, a giant spider, is asleep. Riko and Maki head off to find the Red Water.
At the pool with the Red Water, Godzilla is teaching Minilla monster skills, starting with roars. Minilla’s for now is a high pitched squeal. Godzilla encourages him to create nuclear breath. But he can only create smoke rings. Godzilla steps on the baby’s tail, and Minilla blasts fire. The lesson done, the pair nap. Riko and Maki fill their canteens and leave. They return with the water and administer it to the ailing scientists. With their equipment smashed and giant monsters roaming the island, Kusumi admits it may be time to end the weather controlling experiments.
Riko is gathering herbs and awakens a Gimantis. It knocks her uncoscious, but not before she call for her friend, Minilla. Minilla blows smoke rings at the giant preying mantis, but it only serves to irritate the bug. The fight awakens Spiga. Maki finds Riko, and the pair run to safety. Godzilla arrives to rescue his son. A blast from his nuclear breath cause the Gimantis to run off.
Spiga finds the cave with the humans and traps them with its web. The radio has been repaired, but someone must go outside to erect an antenna. Riko and Maki volunteer. Outside, they spot Minilla, who is fighting with Spiga. Kusumi suggests freezing the monsters. There is just enough of the weather controlling equipment left to do so.
The fight between Minilla and Spiga continues. The giant spider has covered the baby with webbing. The Gimantis shows up and fights with Spiga, who covers it with webbing also. The freezing device is launched. Godzilla wakes from a nap, and finds the three other monsters. Godzilla throws a boulder at it and pulls the baby from the webbing. Spiga tries to cover Godzilla with the web. The scientists blow the weather device, causing the temperature to drop.
Minilla uses its nuclear breath to burn the webbing covering Godzilla, who then blasts Spiga. As the beasts battle, the scientists float off in a life raft to meet the rescue ship. It begins to snow. The weather control experiment is a success!
Godzilla disables the Spiga with his nuclear breath. Both Godzilla and Minilla deliver the killing blow with their nuclear breath, and walk toward the beach. The snow is getting deeper and ice is forming on the ocean around the beach. Minilla trips and falls. The ever patient Godzilla walks back to gather up his son. Together, they hibernate until warmer weather. A submarine arrives to pick up the scientists.
Human Cast: Tadao Takashima (Prof. Tsunezou Kusumi), Bibari Maeda (Riko Matsumiya), Akira Kubo (Goru Maki)
Monster Cast: Godzilla, Gimantis (Kamacuras), Minilla, Spiga (Kumonga)
Notes: The English translation of this movie identifies Kamacuras as Gimantis, and Kumonga as Spiga. Also, Riko is know as Saeko in the Japanese version. The subtitles of the North American DVD identify them with the original names. Minilla is known only as “Baby Godzilla” throughout the North American version of the movie.
LogBook entry by Robert Parson