Doctor Cal Meacham (Rex Reason) is flying to his lab in a Lockheed T-33 Shooting Star Jet. Its engine fails and he is saved by a mysterious green glow. In the lab a device is delivered in parts, called an Interocitor. Cal and his assistant Joe (Robert Nichols) follow the instructions for its construction and a mysterious man named Exeter (Jeff Morrow) appears on the screen and congratulates Meacham on passing the test. He is invited to be part of Exeter’s special research project.
He is pickup up at the airport by a computer-controlled Douglas C-47 aircraft with no windows or pilot. It lands in a remote area of Georgia, where he finds an international group of top scientists, including his old flame Doctor Ruth Adams (Faith Domergue). She does not recognize him, and he is suspicious of the strange-looking Exeter and his cronies. He and Ruth decide to leave with Steve Carlson (Russell Johnson), but their car is attacked, and Carlson killed. Then their aircraft is beamed up into a flying saucer.
Exeter explains that he and his associates from the planet Metaluna are at war with the Zagons. They are running out of uranium to keep their protective energy field intact. They are hoping humans will transmute lead into uranium, but it may be too late. Exeter takes the Earthlings to his world, sealing them into protective tubes to survive the transition. They land on Metaluna, but the planet is being bombarded by meteors from space. The leader of Metaluna, called the Monitor (Douglas Spencer), tells them the Metalunans intend to flee to Earth for safety.
To start with, Meacham and Adams must be subjected to thought transference to subjugate their free will. Exeter thinks this is misguided and immoral, and he helps them escape. Exeter is nearly killed by a bug-eyed mutant as they flee from Metaluna. Behind them, the planet’s protective ionization layer collapses. Metaluna heats up under the bombardment, and the planet turns into a lifeless radioactive sun. Ruth is attacked by the mutant, but it collapses and dies. Returning to Earth, Exeter sends Cal and Ruth home in their aircraft and dies as his saucer crashes into the ocean.
The movie was produced by William Allard and directed by Joseph Newman in 1955, based on the 1952 novel by Raymond F. Jones, published in Thrilling Wonder Stories as three related novelettes. It was praised by critics as an eye-popping technicolor feature with excellent (for the time) special effects and a well-written script. In 1996, an edited version was lampooned on Mystery Science Theater 3000. I was all right with them taking the mickey out of movies in which people were unable to outrun carnivorous plants, but I was offended for This Island Earth, remembering how the mutant scared the bejesus out of me at the age of nine. They called it a myoo-TANT and I was puzzled because I knew perfectly well what a mutant was. I never could figure out if they mispronounced the word for dramatic effect or didn’t know better.
Clips from the film have appeared in the background of at least a dozen films, music videos, and games since. It was filled with ideas stolen later by grander movies. A picture of Earth in the movie was used as the planet Earth in the Universal Pictures opening logo thereafter. Faith Domergue said her pants were so tight that she had to have an assistant help her put them on, and she could not wear underwear. The flying saucer was based on a photograph taken by an Oregon farmer named Paul Trent, who claims to have seen the UFO in 1950. One of the devices in the Ryberg Electronics Lab came from the Universal Frankenstein pictures of the 1940s. In 1960, the film was shown in drive-ins as a double feature with Forbidden Planet. Exeter is the good alien in this strange and even somewhat beautiful little movie. I was intrigued by the idea that we would run into two alien civilizations at the same time, neither of which we would want to hang out with, and that the one alien who knows us best is willing, not only to die, but to let his civilization fall to save us.