 Astronauts Glen and Fuji travel to Planet X, a newly discovered moon of Jupiter, which for some reason has been transmitting radio waves to Earth. While there the two astronauts are then ordered to go down to the the caverns where the people of the planet are forced to go, allegedly because they are now being attacked on a regular basis by Ghidorah, who moved there after being defeated by Godzilla, Rodan and Mothra several months earlier. The aliens then request that they be allowed to "borrow" Godzilla and Rodan (sans Mothra) as a means of repelling Ghidorah and that in exchange they would be given a formula for a "miracle drug" to combat all forms of cancer. In the meantime, Fuji s sister Haruno is dating inventor Tetsuo Torii, who has just invented a high frequency transmitter to ward off muggers. A few weeks later the aliens take Godzilla and Rodan back to their planet and they seemingly defeat Ghidorah. The astronauts then get a tape recording supposedly containing the formula. The tape actually contains an ultimatum for the people of Earth to surrender or else face destruction from the combined strengths of Godzilla, Rodan and Ghidorah. Will the nations of the world give in to the demands of the aliens or will they be destroyed? And what role does Tetsuo s invention play in the upcoming battle?