The Hush of Dark Wings — Charles L. Grant

IS IT -PARANOIA,
Black Oak Security is a crack team of private investigators led by brilliant, enigmatic Ethan Proctor. He is a careful man. Careful in what he says, careful in what he does. And very careful about which cases he takes. But when a letter arrives from a woman he once knew, begging him to investigate strange happenings in her town, Proctor is careless. He takes the case without knowing exactly what he's getting into.

OR PARANORMAL?
Hart Junction, Kansas, is the image of a deserted frontier town. Its claim to fame is being the set for many a grade-B western. But the movies moved out, and a strange cult moved in. Its members seem friendly. Concerned. Cooperative. So why are the townspeople so afraid? Why are so many people missing?

And what are the strange winged creatures seen circling in the sky above town?