The electronic engineer Dr. Cal Meacham is a prominent scientist that is studying industrial application of nuclear energy and also a great pilot. One day, he receives a different condenser and soon his assistant Joe Wilson receives a manual instruction and several components of a sophisticated machine. Carl and Joe build a communication apparatus and a man called Exeter contacts Carl. He tells that Carl has passed the test assembling the Interocitor and invites him to join his research. The intrigued Carl decides to travel to meet Exeter that sends an unmanned airplane to bring him to an isolated facility in Georgia. He is welcomed by Dr. Ruth Adams but she mysteriously does not recall their love affair in the past. They team-up with Dr. Steve Carlson and they note that the other scientists in the facility have been transformed, having a weird behavior. They decide to flee in a car, but they are attacked by rays and Steve dies. Carl and Ruth also witness the facility blowing-up and they escape in an airplane. However they are pulled up into a flying saucer and realize that Exeter is an alien. Whal is the objective of the aliens?
Synopsis by IMDb
Few creatures typify the classic 'bug-eyed alien' stereotype better than the marauding lobster-handed 'Mutant' seen terrorising Faith Domergue in publicity images for This Island Earth. Sadly, budget and time constraints meant he was only properly mutant from the waist up – the planned 'weird alien legs' were ultimately reduced to mere silver trousers on screen. This perennial favourite gave us a race of high-foreheaded brainboxes from the planet Metaluna. Their elevated hairlines would inspire the TV ads featuring the Tefal scientists, who briefly usurped the Cadbury’s Smash Martians as icons.

This Island Earth is an exceptional film for its time. The visual effects were ahead of their time and would provide the basis for effects that would later be used in Star Wars and other, more highly regarded, sci-fi classics. The plot may be muddled and overly complicated, but it vividly reflects the Cold War anxieties of the day and prevailing concerns over the misappropriation of scientific endeavour for military use. This Island Earth is not as sophisticated and well-known as other 1950s sci-fi movies, but it is arguably one of the most important films in the genre.

Just keep in mind that while you're doing whatever you're doing, big-headed creatures from space are watching you and making plans. Well, at least they are in this better-than-average science fiction movie.
For reasons that defy logic, the excellent This Island Earth was held up for ridicule as an allegedly bad movie in the film version of TV's Mystery Science Theater. If not the best science-fiction film of the 1950s, Earth is certainly one of the most intelligent and elaborate. The story begins when the image of Exeter (Jeff Morrow), a huge-domed scientific genius from the planet Metaluna, appears on an experimental 3D television screen. Exeter invites several noted scientists from around the world to work on a top-secret project at Exeter's earthly mansion. Among those accepting the invitation are Cal Meacham (Rex Reason) and his ex-fiancee Ruth Adams (Faith Domergue). Soon, Cal and Ruth learn Exeter's true motives; to use the Earth's atomic knowhow in building a defense shield to protect Metaluna against the enemy planet Zahgon. Eventually, Exeter boards his high-tech flying saucer and whisks Cal and Ruth off to his dying planet, where, among other perils, they are menaced by a hideous mutant. Based on a novel by Raymond F. Jones, This Island Earth is one of those rare 1950s speculative films that holds up as well today as it did when first released, despite the comparative quaintness of the special effects and high-tech paraphernalia. Incidentally, the climactic Metalunan scenes were directed by Universal's resident sci-fi specialist, Jack Arnold.
So, if the real stars of the picture will step forward, we have; Clifford Stine, William Fritzsche, Alexander Golitzen, Richard H. Riedel, David S. Horsley, Russell A. Gausman and Julia Heron, technical artists.
It is very hard to rationalize and rate such a campy film, but I will do it regardless with a very enthusiastic 5 out of 5.Let your guard down and enjoy yourself!
From A French Restored