Several nuclear physicists arrive at a South Seas island at the behest of Dr. Yamazaki. Leaving their families aboard a ship anchored in the harbor, Yamazaki shows her guests her facilities, including a nuclear reactor. She shows them her crowning achievement, a giant monster which she releases into the sea. The beast destroys the anchored ship. Dr. Yamazaki has the outraged scientists removed by her guards.
The monster heads away from her island. In Australia, Godzilla stands on Manly Beach, apparently sleeping while the Australian army and G-Force observe him. While watching Godzilla, reports come in that something big is headed toward them. Dr. Yamazaki's monster attacks Godzilla and the monsters' battle takes them inland, into Sydney. Godzilla finally kills the other monster and heads back to sea. Back on Lord Howe Island, Dr. Yamazaki plans her next creation.