**_Slow slasher set in Savannah pays off with the last act_** A teacher of deaf kids is haunted by her upbringing with her crazy twin sister. When it’s discovered that she’s escaped the institution, people around her start dying. This builds up to the sisters’ birthday. While technically an Italian production, “Madhouse” (1981) was shot in America with American actors and is also known as “There Was a Little Girl.” While the first hour is mostly unhurried drama, this is the foundation for the crazy last act. The producer/director/writer Ovidio G. Assonitis gives hints of what’s really going…