I got this cheap on eBay, and for once I wasn't disappointed. The movie opens up with an explantion of the Merrye Syndrome. In late childhood, Merrye family members begin to regress in age, possibly attaining a pre-human mental state pf savagery and cannibalism. We then see the postman driving down a street, trying to find the Merrye house. When he does, Virginia (one of the Merrye children) catches him in her spider web and "stings" him to death. When Bruno (Lon Chaney, Jr.), the chaffeur and now the head of the household, comes home, he's disappointed to see Virginia has "hurt" another person. "It makes people wonder about us, and your father wouldn't like that." Ralph (Sid Haig), the 6-foot-toddler, finds a letter in the dead postman's hand. It seems the two remaining Merrye family relatives want to take over the property and institutionalize the children.
The relatives, along with a lawyer and his secretary, come and have dinner with the family. Cousin Emily and the lawyer decide to stay the night, but the secretary wants to go to a hotel. She and Peter (Emily's brother) go to an Inn and drink most of the night. Meanwhile madness ensues back at the Merrye House. Emily is dancing in lingerie in front of the mirror and discovers Ralph hanging upside down outside the window, watching her. The lawyer snoops around the house and ends up getting himself "hurt."
Peter and Ann come back later. Elizabeth takes Ann up to father's room, while Virginia plays spider with Peter. All this leads up to an interesting ending, which I will not spoil for you.
I don't know why people say this is a cannibal movie, because it's not. There's a scene at the end where the older relatives may be eating Emily, but most of the main characters are vegetarian(!). The acting was pretty good overall, but the few special effects were horrible. Thankfully we don't see many shots of gore or of the deformed family members in the basement. Anyway i thought it was a unique movie, with a decent story and overall i enjoyed it.