Because you don't understand it, you want to kill it.
An alien ship crashes into the desert, at first it's thought to only be a meteorite, but small time scientist Richard Carlson gets to view the stricken ship before it is totally buried beneath the collapsing crater it created upon its crash landing. Nobody believes Carlson, but soon the aliens start taking on human form and it's then that everyone else must sit up and take notice before it's deemed too late.
It Came From Outer Space stands as one of the better sci-fi pictures to come out of the Cold War 1950s. Based on the Ray Bradbury story "The Meteor", the story leans heavily on anti-conformist themes and confidently trumpets something different to ourselves actually having the damn right to be different, and that is something I can personally truck with. As with most of the other films from the sci-fi/alien genre, "it" perfectly captures the paranoia of the people, the sense of mistrust befitting the atomic age, the fear of the desert never more evident than it is here.
Directed with some style from genre guru "Jack Arnold" ("This Island Earth"/"The Incredible Shrinking Man"), the film was originally shot in 3D, and though sadly I have never been able to see the picture in that format, I can certainly imagine greatly the impact that certain scenes would have had. The picture is also notable for the use of POV shooting from the alien perspective, all fuzzy focus from a spherical single eye, it works real well and would be something that many other film makers would use from here on in.
This is not a film that relies on creatures to see it home safely, in fact we barely glimpse the creatures here, but we don't need that to be the case, for they make their mark regardless, all of which leaves It Came From Outer Space as a very knowing and quite often intelligent piece of work. 8/10