Deranged (1987)

"The ultimate horror comes from within."

Joyce seems to have the perfect life - she lives in a nice apartment with a wealthy husband, is soon going to give birth to a baby boy, and has all the money she'll ever need. But while her husband is away in London on business, Joyce is attacked by a masked intruder, that unleashes within her a frightened little girl, haunted by her "special" relationship with her daddy, and a crazed madwoman who is hungry for revenge. From then on, Joyce's wild hallucinations take over, and she begins to murder anyone and everyone who comes near her, in a violent fit of rage.