| Director | Ishirō Honda |
|---|---|
| Box office | $1 million |
An evil mad scientist named Dr. Who creates Mechani-Kong, a mecha modeled after the legendary Mondo Island giant ape named Kong, to dig for Element X, the highly radioactive mineral found only at the North Pole. As Mechani-Kong enters an ice cave and begins to dig into a glacier, the Element X radiation destroys its brain circuits, causing Mechani-Kong to shut down. Who then sets his sights on getting the real Kong to finish the job. Who is taken to task by a female overseer, Madame Piranha, whose country's government is financing Who's schemes, and frequently berates him for his failure to get results.
Meanwhile, a submarine commanded by Carl Nelson arrives at Mondo Island, where Kong lives. Kong gets into an intense fight with a giant dinosaur named Gorosaurus and a sea serpent. He falls in love with lieutenant Susan Watson, while Who subsequently goes to Mondo Island to abduct Kong and brings him back to his base at North Pole. Kong is hypnotized by a flashing light device and fitted with a radio earpiece. Who commands Kong to retrieve Element X from the cave. Due to the problems with the earpiece ensue, Who kidnaps Watson, who is the only person who can control Kong.
After Watson and her fellow officers are captured by Who, Piranha unsuccessfully tries to seduce Nelson to bring him over to her side. Eventually, Kong escapes and swims all the way to Japan where he battles Mechani-Kong in Tokyo. As two monsters face off at the Tokyo Tower, Kong prevails and destroys Mechani-Kong and kills Who and his henchmen. In the end, Kong triumphantly swims back to Mondo Island.