Protecting the Earth From the Scum of the Earth

Charlie and Rhonda are a sweet and comfortable married couple on vacation with their lovely daughter Daphne. They find a rundown boarding house and its haggard owner, Joseph, an ex-con whose mother has just died and left him the property. He doesn't know why this cheerful couple would want to vacation in the worst part of Los Angeles, but he doesn't know they're visitors from outer space, and their idea of fun is murdering and eating humanity's worst.