An urgent bomb-threat radio message immediately throws a routine flight into chaos. co-pilot Sugisaka, Teruo Yoshida, orders a baggage check, while stewardess Kuzumi, Tomomi Satō, opens an unattended suitcase under a bench and discovers a rifle. The man with no bag pulls a gun on Sugisaka and forces the pilot to steer toward Okinawa. He shoots the plane’s transistor radio just as news reports a UFO over Japan, with Japanese and U.S. Air Force fighters in pursuit. A luminous object streaks across the sky, disables the aircraft’s controls, and ignites an engine fire. The plane crashes on an uncharted, deserted island.
Only a handful survive: Sugisaka; Kuzumi; Mrs. Neal, Kathy Horan; Senator Mano, Eizō Kitamura; Tokiyasu, Nobuo Kaneko, and his wife Noriko, Yūko Kusunoki; Dr. Momotake, Kazuo Katô; and space biologist Sagai, Masaya Takahashi; plus the teenage caller. The hijacker slips into the jungle, coming upon the wrecked ship, and as he steps into a clearing, a dark ooze creeps toward him and splits his forehead open, sending Kuzumi into unconsciousness.
Sugisaka retrieves the injured Kuzumi. Dr. Momotake hypnotizes her to recount the jungle sequence. The teenager who made the threat attacks Momotake, pushing him off a cliff, where the investigator encounters the hijacker who drains his blood.
At dawn, the hijacker reappears, lying on the ground with a long scar on his forehead. The survivors bring him inside and tend his wound. Tokuyasu, Nobuo Kaneko, uses the rifle to force everyone out of the plane and locks himself in with the hijacker. Moments later, Tokuyasu’s screams are heard, and the door opens to reveal his dead body, drained of blood. The hijacker reappears and carries Noriko off toward the spaceship. Sunrise shows Noriko standing on a ridge, and her voice speaks with the cadence of the alien Gokemidoro. It is revealed that the Gokemidoro has invaded Earth to eradicate humanity. Noriko then plummets from the ridge, shriveling into a cadaver.
The survivors debate whether extraterrestrials would invade Earth. Sagai theorizes that the hijacker turned into a vampire. Mano, Eizō Kitamura in spirit but not in name, challenges them to prove vampires exist and suggests sacrificing someone to the Gokemidoro. The survivors shove the teenage caller outside as the hijacker advances; the teen triggers the bomb, blowing a large hole in the aircraft, wounding Sagai. Mano escapes with Mrs. Neal, but the hijacker closes in. Mrs. Neal fires several shots but misses, and the hijacker kills her.
Mano slips back to the plane while the hijacker remains close. Sugisaka hurls a bucket of aviation fuel at the hijacker and sets him on fire. The Gokemidoro crawls from the burning body, enters Sagai’s forehead, drains Mano, and then turns toward Sugisaka and Kuzumi, who manage to flee. Sagai is swept off a hill by a landslide, then returns to the spaceship. The Gokemidoro finally emerges, reducing Sagai to dust.
Sugisaka and Kuzumi reach a highway and find the city deserted; every human seems to be dead. The Gokemidoro’s dark pronouncement rings out: no one will be spared.
In the epilogue, Sugisaka and Kuzumi wander across a rocky landscape, while a fleet of Gokemidoro spaceships hovers in orbit around Earth, awaiting the order to attack.
