A huge flaming meteor splashes into the Pacific Ocean in the Ogasawara Trench, near Godzilla. It creates a typhoon that reveals a giant, rainbow colored egg. Takuya, Masako, and Kenji are sent to recover the egg on Infant Island. Meanwhile, another creature with red glowing eyes and a high pitched screech is awakened.
After several days, the team finds a cave with ancient paintings, one of which includes a butterfly and some sort of bat-like creature. The three press on and find the egg. Two women, less than a foot tall, calling themselves The Cosmos, tell the team the egg is Mothra. 12 thousand years earlier, and advanced civilization had created a weather machine, which had greatly offended the Earth. The Earth sent a monster, Battra, to destroy the humans. Mothra however defeated Battra, who had been sleeping in the sea. But pollution was threatening to bring Battra back.
The CEO of the Marutomo Corporation puts plans in motion to bring the egg to Japan. The Cosmos volunteer to go also. A larval form of Battra, however, is already on its way. Burrowing underground, Battra arrives in Nagoya and tears through the city. Lightning bolts from it’s eyes and a horn on its head easily render the Japanese Defense Force irrelevant. Battra destroys much of Nagoya, and burrows underground again.
The ship pulling Mothra’s egg behind it encounters Godzilla near the Philippines. As the King of the Monsters approaches, the egg hatches! The Mothra larva escapes before Godzilla can destroy it with his nuclear breath. Mothra distracts Godzilla in an attempt to let the ship slip away. Battra arrives and battles both of the other monsters. Battra and Godzilla fight underwater. Thier fight is interrupted by a volcanic eruption, and it’s believed they are killed in the molten rock. Mothra returns to Infant Island and the ship continues to Japan. Once there, Ando steals the Cosmos, with plans to exploit them for marketing purpose by the Marutomo Company. Locked away, the Cosmos sing out to Mothra, who begins the journey to Japan to rescue them.
Attempts to stop Mothra are useless. The larva destroys the Naval aramada sent against it. On its way to rescue the tiny girls, it is no respecter of property and smashes through the city. Takuya and Masako find the girls. Finding they are safe, Mothra leaves. But as it does, the giant larva collapses onto the capital building and encases itself in a cocoon.
Volcanic Mount Fuji explodes. Ando, who has had a change of heart, tells the CEO of the Marutomo company the Earth is getting its revenge for the damage caused by humans, and walks out.
Godzilla rises from the volcano and heads towards Tokyo. Back at the capital building, Mothra emerges from the cocoon as a giant, beautiful, rainbow colored butterfly. She spreads her wings and flies off to battle Battra. Meanwhile, out to sea, the larval Battra transforms into a giant bat and flies off. JDF units wage a fierce, but futile, battle in an attempt to change Godzilla’s direction.
As Godzilla approaches, Mothra and Battra meet in the sky over Yokahoma. Godzilla crashes through the city while the flying creatures do battle. Battra forces Mothra to the ground at a theme park in the harbor area. Godzilla finds the others and is attacked by Battra. Using it’s lightning blasts, Battra drops a building on the giant lizard. The King of the Monsters rises from the rubble, grabs Battra, and flings it to the ground. He blasts at it with his nuclear breath. Lightning from the injured Mothra stuns Godzilla. She flies to Battra, who gives her renewed energy.
Mothra rises to attack the approaching Godzilla. Using lightning blasts and glittery dander from her wings she appears to win the battle, but Godzilla is able to beat her back with a nuclear pulse. She crashes into a ferris wheel, but Battra grabs it before it can crush her. Battra slams the wheel into Godzilla, who falls to the ground. Both flying beasts blast at Godzilla from above. Godzilla tries to defend himself, but is confused by the onslaught. He struggles against the dander and the lightning before falling in a heap.
Battra grabs Godzilla, who bites into its neck. Mothra grabs onto Godzilla’s tail. The two carry the monster away from the battlefield. Battra is bleeding profusely from the neck bite, and Godzilla blasts at him with his nuclear breath, killing the giant bat. Mothra releases its grip on Godzilla’s tail and drops the pair into the ocean.
Keeping a vow with Battra, Mothra leaves the Earth to change the course of an oncoming planet-killing asteroid, a possibly deadly task that Battra would have performed if Godzilla had not reappeared.
screenplay by Kazuki Omori
directed by Takao Okawara
music by Akira Ifukube
Human Cast: Testuya Bessho (Takuya Fujita), Satomi Kobayashi (Masako Tezuka), Takehiro Murata (Kenji Andoh)
Monster Cast: Godzilla, Mothra, Battra
LogBook entry by Robert Parson