Doctor Russell Marvin (Hugh Marlowe) and his new bride Carol (Joan Taylor) are driving to work when a flying saucer appears above them. Doctor Marvin is in charge of Project Skyhook and has launched ten research satellites into orbit, but he is hesitant about revealing what he saw. General Hanley (Morris Ankrum), Carol’s father, informs him that several satellites have fallen back to Earth. In fact, Marvin has lost contact with all of them, and he fears the aliens are responsible.
When a saucer lands the next day near Skyhook, aliens in metallic suits appear and the infantry opens fire, killing one alien, though the others are quickly protected by a force-field. The aliens proceed to kill nearly everyone at Skyhook. The General is captured and taken away in a saucer. Too late, Marvin decodes a message that the aliens want to talk. Instead, Earth forces met them with violence. Marvin contacts the aliens and goes to meet them, followed by Carol and by Major Huglin (Donald Curtis). All of them, plus a cop pursuing them (Larry Blake), are taken aboard the saucer, where the aliens extract knowledge from the General’s brain.
The aliens say they are the last of their species and have fled their destroyed solar system. They are old and only their clothing keeps them alive. They shot down the satellites, thinking they were weapons. Then they sink a Naval Destroyer to show their power. Horrified by their cold brutality, Carol begins to break down, and the officer pulls his gun, whereupon the aliens seize control of his mind. The aliens say they will all be released eventually. Marvin tries to remain calm as Carol becomes irrational. The Major and the Marvins are released to tell the world leaders to meet with the aliens in Washington 56 days from then to negotiate the occupation of Earth.
Marvin discovers the secret of the aliens’ protective suits and develops a counter-weapon against the saucers. The General and the patrolman are jettisoned from the saucer, falling to their deaths. The saucers attack Washington, Paris, London, and Moscow before Doctor Marvin’s secret sonic weapon proves decisive against them. Then the Marvins continue their honeymoon.
Ray Harryhausen animated the flying saucers and all the falling masonry, which he said he would never do again as it was so time-consuming. The saucers were suspended on piano wires, which Harryhausen had to paint out frame by frame. The Earth military shots were mostly stock footage. The destroyer lost was the HMS Barham, which sank in 1941. It was kept secret so as not to upset the British public. A Scottish medium, Helen Duncan, revealed the sinking in a séance and was the last person to be tried under the British Witchcraft Act. Though the film received some pretty bad reviews and was Ray Harryhausen’s least favorite of all his movies, it was copied extensively by later saucer films. Mars Attacks was an affectionate lampoon of Earth vs. the Flying Saucers.
Paul Frees voiced the aliens by jiggling an analog reel-to-reel tape to make the voices slow down or speed up. He was also the voice of the host of the Haunted Mansion ride at Disneyland and did many of the voices for the Bullwinkle Show. One of the shots was from the opening credits of The Day the Earth Stood Still. One of the screenwriters, Bernard Gordon, was listed as Raymond T. Marcus because of the Hollywood blacklist. His real name finally appeared when the movie was released on video.