Reporter Naoko is interviewing members of a UFO club when a large meteor lands in Kurobe Valley. Meanwhile, her detective brother Shindo is assigned to protect the foreign Princess Salno, only for her to be seemingly assassinated before her arrival in Japan. While the meteor is investigated, Salno emerges under the guise of a Venusian prophetess and catches the attention of Naoko and Mothra's fairies. She prophecies the return of Godzilla, Rodan, as well as the arrival of a powerful space monster called King Ghidorah. As Shindo and Naoko protect Salno, the infant Mothra must persuade Godzilla and Rodan to set aside their differences and save the world from Ghidorah.