Scientist Dr. Russell Marvin and his new bride Carol are driving to work when a
flying saucer appears overhead. With no proof of the encounter other than a tape recording of the ship's sound, Dr. Marvin is hesitant to notify his superiors. He is in charge of Project Skyhook, an American space program that has already launched 10 research satellites into orbit. General Hanley, Carol's father, informs Marvin that many of the satellites have since fallen back to Earth. Marvin admits that he has lost contact with all of them and privately suspects
alien involvement. The Marvins then witness the 11th falling from the sky shortly after launch. When a saucer lands at the Skyhook facility the next day in front of the main building, a group of aliens in metallic suits exits with one alien walking peacefully into the entrance of the building, while being fired upon by the infantry guards, killing the one alien, while the remaining aliens and saucer are protected by a
force field. After retrieving the body of the dead alien, the saucer lifts off, returning the fire and spreading destruction across the facility, and killing everyone but the Marvins, who were trapped below ground. General Hanley is captured and taken away in the saucer. Too late, Russell discovers and decodes a message on his tape recorder. The aliens just wanted to meet with Dr. Marvin and for that purpose landed at Skyhook, where they were met with violence. ("Shoot first, ask questions later.") Marvin contacts the aliens by radio and sneaks away to meet them, followed closely by Carol and Major Huglin. A pursuing motorcycle patrol officer and they are taken aboard a saucer, where the aliens have extracted knowledge directly from the general's brain. The aliens explain that they are the last of their species, having fled from their destroyed star system. They are extremely aged and are kept alive only by their protective garments. They have shot down all the launched satellites, fearing them as weapons. As proof of their power, the aliens give Dr. Marvin the coordinates of a naval destroyer that opened fire on them, and which they have since destroyed. Horrified by the cold, unempathetic nature of the aliens, Carol begins to break down, and the patrol officer, despite an attempt by Marvin to stop him, pulls his revolver and fires on the aliens; the aliens subject him to the same mind-control process as General Hanley. The aliens state that they will eventually return Hanley and the patrol officer. As the interaction continues, Carol becomes increasingly irrational, while Dr. Marvin tries to remain calm. Major Huglin and the Marvins are released with the message that the aliens want to meet with the world's leaders in 56 days in
Washington, DC, to negotiate an occupation of Earth. Dr. Marvin's later observations lead to the discovery that the aliens' protective suits are made of solidified electricity and grant them enhanced
auditory perception. Marvin develops a counter-weapon against their flying saucers, which he later successfully tests against a single saucer. As they escape, the aliens jettison Hanley and the patrol officer, who fall to their deaths. Groups of alien saucers then attack Washington,
Paris,
London, and
Moscow, and resistance by conventional weapons is futile, but they are destroyed by Dr. Marvin's sonic weapon. The defenders also discover that the aliens can be easily killed by
small-arms gunfire when they are outside the force fields of their saucers. Upon repelling the attack and no further threats anticipated, Project Skyhook is re-established with Dr. Marvin once again placed in charge. ==Cast==