Dr. Russell Marvin and his wife Carol stumble upon a UFO while en route to the Skyhook military and scientific base. They soon discover that U.S. satellites have been crashing, not from Cold War adversaries, but from extraterrestrial beings concerned about invasions of their own planets. The aliens attempt to land at the base, but the guards, in a panic, open fire on them. The aliens respond with retaliation, leading to an all-out war between the two worlds.