Was cleaning up some old memory sticks and came across the 1973 Movie: "The Baby". Here is a synopsis for those unfamiliar with the movie:
The Baby - Full plot and spoiler
Ann Gentry (Anjanette Comer) is a social worker, whose husband has been involved in a car crash, and takes up the case of the twisted and mysterous Wadsworth family, and takes a special interest in a member only called "Baby" (David Mooney/Manzy), a mentally-ill twenty-something who still acts and is treated like an infant by his mother and sisters. Ann is interested in Baby and wants to have his case for her own. The Wadsworth clan has been neglectful and abusive to Baby, but Mrs. Wadsworth (Ruth Roman) has been extremely overprotective of him ever since his father left shortly after his birth, and isn't going to let another caregiver mess with her son.
Ann tries to convince her that Baby can learn something, but he doesn't look to be able to even pick up and return a ball. When one of his sisters, blonde Alba (Suzanne Zenor) hits him, in sheer frustration of Baby's baby-like behaviour, it's Mrs Wadsworth who defends him, beating Alba in turn. The remaining sister, Germaine (Marianna Hill) sleeps naked with him, as Baby is physically an attractive young man. Ann visits a school of "extraordinary children", and looks how several children play and intereact together, and that makes her feel sad, because of the comparison with Baby.
The sisters throw a party for some friends, and Baby is around on the dancefloor, displaying his childish behaviour. None of the Wadsworth sisters' friends pay any attention to him. Mrs Wadsworth talks about her runaway husband, and she feels quite satisfied that Baby will never suffer such disappointments. Ann gets dizzy after drinking a cup of punch. Alba and Germaine take her downstairs and tie her down. Baby is with Ann, but he doesn't seem to understand what happens. In fact, when Ann tries to release herself he starts to cry. The sisters are making out with their loser boyfriends. Baby has to be bathed, but Ann finally dresses him up in a suit. Ann takes photographs of Baby dressed as an adult, and shows them to his family.
Eventually, Ann and her mother take Baby, and his mother and sisters come after them, but Ann and her mother kill them, and we finally find out why she is so interested in Baby.