This is director Jack Arnold's first science-fiction effort and one of the earliest to use a desert setting. Richard Carlson is very believable as an astronomer who, along with his fiancée (Barbara Rush), witnesses a meteor crash-landing that turns out to be a spacecraft. No one in the small town believes him until disappearances occur. At one point, Carlson discovers his closet has been ransacked and wardrobe stolen!
Arnold uses Theremin music to great effect, the photography is eerie, dialog (by Ray Bradbury) poetic, and the alien is a large crawling mass with one bulging eye that leaves a snail-like trail in its path. Incognito as humans so as not to terrify earthlings with their unique physicality, the aliens are NOT bent on destruction - an interesting precursor to Steven Spielberg's expensive "Close Encounters of the Third Kind" (1977) - even its main titles are also at the end.
In an unconscious insight into social behavior, a scene has Carlson speaking to the sheriff (Charles Drake) while watching a spider on the desert ground ("...Why are you afraid of it? Because it has 8 legs, its mouth moves from side to side, instead of up and down? What would you do if it came towards you?"). The sheriff squashes it. This holds true for animals, as well as people (who have different coloring, etc.), avoiding, ridiculing, harming or destroying, sadly. The classic Twilight Zone episode "Eye of the Beholder" (1960) is a fine example: most of the "monsters" in these science-fiction/horror films just look different than humans, we might be "monsters" to them. This is low-key, intelligent, satisfying drama. Russell Johnson, Joe Sawyer, and Kathleen Hughes co-star.