Baby Jane Hudson (Bette Davis) is an unstable former child star who believes that she's responsible for crippling her sister, Blanche (Joan Crawford), a famous adult star. Now, it's twenty-years after the incident and they live, isolated, in an old mansion. Baby Jane clearly has mental problems, living in the past, and she begins to treat her older sister more cruelly as the film progresses. She learns that Blanche is out of money and needs to sell the house and in response isolates her by preventing her from making phone calls. She also kills her pet bird and tries serving her a dead rat for dinner. Things get worse. As Blanche slowly starves to death, unable to escape, Baby Jane starts planning, deluded, for a new life. She puts an add in the local paper for a creative partner to do an act with and finds Edwin Flagg (Victor Buono), who is clearly agreeing to do this for the money. Eventually the film culminates with one of the sisters dying.
This movie is a great character study and horror movie/psychological thriller. If you plan on watching the recent series FEUD: BETTE & JOAN you need to watch this movie first, as the series is primarily about the actress' teaming up for this film. Both the original movie and the TV series are highly recommended.