In the early 1950's a huge meteorite crashes to Earth in southern California, and a Manhattan Project scientist, Dr Clayton Forrester, races to the impact site. He discovers that the meteorite is slightly radioactive, and far too hot to approach, so decides to return with some colleagues the following day to examine it. But during the night the "meteorite" opens, and three people who had stayed at the site to keep the curious away are vaporized by an unearthly "heat ray!" With reports coming in that "meteorites" are landing all around the World, Dr Forrester realizes that the Martian invasion of Earth has begun, and mankind will have to fight for its very survival!