The "Silent Invasion" Mythos
It was supposed to work like this: the aliens would furnish the government with a list of their human abductees, never going over quota. But soon the horrible truth became apparent: the aliens were abducting more than their legal share of unwitting humans. And to top it off, they were performing grotesque biological experiments with cattle and leaving their handiwork in plain view. Moreover, some of the abductees weren't coming back . . .