The Baby (1973)

The Baby is a 1973 American horror-thriller film directed by Ted Post and written by Abe Polsky. The film stars Anjanette Comer, Ruth Roman, Marianna Hill, Suzanne Zenor, and David Manzy.

Plot
A social worker tries to rescue an adult baby from his very creepy family in this essential ‘70s cult classic. Ann is determined to help “Baby”, who she suspects is being kept in his infantilized state by mean mommy Ruth Roman. But the more Ann tries to play miracle worker, the more she puts herself in grave danger. Mommy likes things just as they are!