In southern California, Dr. Clayton Forrester (Gene Barry), a well-known atomic scientist, is fishing with colleagues when a large object crashes near the town of Linda Rosa. At the impact site, he meets USC library science instructor Sylvia Van Buren (Ann Robinson) and her uncle, Pastor Matthew Collins (Lewis Martin). Later that night, a round hatch on the object unscrews and opens. As the three men standing guard at the site attempt to make contact while waving a white flag, a Martian heat ray weapon obliterates them. The United States Marine Corps later surround the crash site, as reports pour in of identical cylinders landing all over the world and destroying cities. Three Martian war machines emerge from the cylinder. Pastor Collins attempts to make contact with the aliens, but he is disintegrated. The Marines open fire, but are unable to penetrate the Martians' force field. The aliens counterattack with their Heat-Ray and skeleton-beam weapons, sending the Marines into full retreat.