As a child, Jane Hudson (Bette Davis) was a pampered vaudeville star known to the world as Baby Jane while her younger sister, Blanche (Joan Crawford), led a quiet life in her considerable shadow. Decades have passed and now Blanche is a beautiful, talented movie idol and Jane a lowly extra. When a car accident cripples Blanche, binding her to a wheelchair, Jane sees her opportunity for revenge and assumes the role of caretaker. Her newly gained power completes the transformation of the sugar-sweet child star into a nightmarish caricature of Baby Jane. As she does everything she can to make her sister's life a living hell--including feeding Blanche a dead rat and brutally beating her when she tries to phone for help--Jane plots a comeback, aided by shifty musical director Edwin Flagg (Victor Buono).