Some time last year, I read about a Twilight Zone episode from the 60's (I think!). It was about a person that comes to a town, and that town becomes more and more surrounded by a dark cloud. This cloud is the town's negative and destructive feelings, and the inhabitants are not able to leave due to this cloud surrounding the town and keeping them in. That's what I remember of the synopsis, anyway; I haven't been able to find it later.
After reading this, I couldn't help but instantly think of Darkness (the song) - there are just too many similarities for it to be a coincidence.
Does sound familiar to anyone?