Not one of the more memorable AIP sci fi-ers of the late 50s - it lacks high camp, and isn't dumb so much as dull. Roger Corman helped make it (in an uncredited producing capacity) and the cast is headlined by Ed Nelson (who has star quality, albeit TV star quality). It's a sort of Invasion of the Body Snatchers knock off, with a mysterious alien space craft causing some locals in a small American town to turn into zombies. (Apparently the story plagiarised from a Robert Heinlein short story, "The Puppet Masters" which was from 1951 and probably inspired Body Snatchers.)
There's some spooky moments with the creatures running wild and the story isn't bad, despite plot holes (an alien ship has landed, the government know about it and only send in a couple of men). The climax is quite spectacular for a low budget movie - and quite shocking with Ed Nelson going on a suicidal mission. But the direction fails to add much suspense or atmosphere and even at a little over an hour I found this dragged. Leonard Nimoy pops up towards the end as the doctor - he's in makeup so I didn't identify him. The cast also features late 50s teen girl regular Jody Fair.