Dr. Clayton Forrester (Gene Barry) is a scientist spending a vacation in a small town in California when a meteor lands in the hills nearby. But this is actually the first step in an invasion of Earth by the forces of Mars, who are soon sweeping across the land in their unstoppable war machines. Dr. Forrester barely escapes the slaughter with Sylvia Van Buren (Ann Robinson), another survivor from the town, and both make their way to Los Angeles as humanity's hopes for survival grow ever dimmer.