Senator Howard K. Perkins goes on the air to announce that the Northwest U.S. has been stricken by a plague of muteness. Nicknamed "The Great Silence," the plague has been spreading steadily ever since and will reach the East Coast within 24 hours. Government scientists believe that hydrogenic particles caused by nuclear bomb detonations are responsible and will soon fade.
In the Northwest U.S. in the Bitterroot Mountains, Paul and his wife Mathilde live in a crude cabin deep in the woods. Both have been rendered mute by the plague, and try to communicate as best they can. Mathilde finally makes it clear that she wants Paul to go out and go hunting, and Paul grabs his rifle and heads out. As he checks his empty traps, Paul finds a metallic three-fingered glove on the ground. Shocked, he tosses it on the ground and hears a strange buzzing noise. Going to investigate, Paul finds a strange alien spaceship in the woods, spouting a white mist from the top. Paul peers in the porthole and sees a diminutive alien creature studying a map of the U.S. and marking out the progression of the plague.
Paul goes back to the cabin and tries to tell Mathilde what he's seen. She doesn't understand and Paul grabs a cup and a saucer and tries to demonstrate the alien craft flying through space. Mathilde wonders if he's been drinking and checks his breath, and then checks Paul's temper. Paul sits down in frustration as Mathilde goes to get water, and turns on the radio. He listens as Perkins announces that the mist is reaching Washington and then cuts off, and Paul realizes that the white mist from the spaceship is causing the Great Silence.
Desperate, Paul goes to the commissioner's office in nearby Kenasha and "talks" to the sergeant on duty. The sergeant indicates that Paul should write down what he wants, but Paul doesn't know how to read or write. Having enough, the sergeant lets Paul in to see the commissioner and the mountain man tries to mime the alien. The commissioner doesn't understand and shows him a series of cards telling Paul that there's nothing to worry about and the plague will soon end. Frustrated, Paul uses a globe of the world and an American flag to demonstrate how the alien ship flew down from the stars and land on the planet, and the commissioner's cigar to indicate the mist. The commissioner figures that Paul is panicking from the plague and has the sergeant escort him out.
When Paul goes back to the cabin, Mathilde comes in and tries to reassure him. It doesn't help and when she goes to get more water, Paul smashes the cup and saucer in frustration. He then gets an idea and takes some dynamite out of his trunk, and then goes back to the spaceship. The mist is still spreading and Paul buries the dynamite at the base of the craft.
Mathilde returns to the cabin and discovers that Paul is gone. She sees the broken saucer and the open trunk, and goes after Paul.
Paul finishes burying the dynamite and lights the fuse. However, as he backs away he steps into one of his traps, trapping himself.
Mathilde hears the buzzing sound just as the dynamite goes off. She makes her the way to the clearing and finds the debris from the spacecraft. Paul is lying nearby and Mathilde calls her name as the effects of the mist fade. Her husband wakes up and covers her ears rather than hear her screeching, and then assure her that everything is all right.