American Repoter,Steve Martin, is brough to a hospital with dozens of maimed and wounded citizens. In flashback, Martin recalls stopping over in Tokyo, where a series of ship disasters catches his attention. When a survivor finally washes up on Odo Island, Martin flies there for the story with Tomo Iwanaga, a representative of the Japanese security forces and learns of the island inhabitants' belief in a sea monster god known to them as "GODZILLA", which thay believe is causing the disasters.
Martin returns to the island with Dr.Yamane, who leads an investingation crew to Odo Island, where radioactive footprints and a Trilobite are discovered. An alarm rings and Martin, the villagers, and Dr. Yamane's crew head to a hill for safety, only to come across GODZILLA. Dr.Yamane returns to Tokyo to present his findings and concludes that GODZILLA was resurrected by repeated nuclear tests. Martin contacts his old friend, Dr. Daisuke Serizawa, for dinner but refuses due to plannes commitments.
Emiko, Dr. Yamane's daughter, goes over to Serizawa's to break off her arranged engagement to him, due love for Hideo Ogata, a salvage ship captain. However, Dr, Serizawa gives her a demonstration of his recent project which horrifies her and is sworn to secrecy while unable to break off the engagement. GODZILLA surfaces from Tokyo Bay and attacks the city. The next morning, the JSDF construct a line of tall electricall towers along the coast of Tokyo to use against GODZILLA.
GODZILLA resurfaces that night and breaks through the electrical fences. Martin documents GODZILLA'S rampage via tape recorder and is nearly killed during the attack. The flashback ends and Martin wakes up back in the hospital with Emiko and Ogata. Horrified by the destruction, Emiko reveals Dr. Serizawa's Oxygen Destroyer to Martin and Ogata, which disintergrates oxygen atoms and the organisms die of a rotting asphyxiation. Emiko and Ogata go to Dr. Serizawa to convice him to use the Oxygen Destroyer but initially refuses. After watching a program displaying the nation's current tragedy, Dr Serizawa finally gives in to Emiko and Ogata's pleas.
A navy ship takes Ogata and Dr. Serizawa to plant the device in Tokyo Bay. After finding GODZILLA, Dr. Serizawa unloads the device and cuts off his air support, taking the secrets of the Oxygen Destroyer to his death. The mission proves to be a success but many mourn at the unexpected loss of Dr. Serizawa. Martin ends the film by saying,"The menace was gone, so great man. But the whole world could wake up and live again".
