Spider Baby

In a dilapidated rural mansion, the last generation of the degenerate, inbred Merrye family lives with the inherited curse of a disease causing them to mentally regress from age 10 or so as they physically develop into prehuman savagery and cannibalism. Merrye children Elizabeth (Beverly Washburn), Virginia (Jill Banner), and Ralph (Sid Haig) are guarded by chauffeur Bruno (Lon Chaney Jr.), who covers their indiscretions as they terrorize passersby through the gates. Trouble arrives with greedy distant relatives and their lawyer seeking to dispossess the family of its home.