Halloween

On Halloween in Haddonfield, Illinois, having already exhibited signs of psychopathic tendencies, ten-year-old Michael Myers murders a school bully, his older sister Judith, her boyfriend Steve Haley and his mother's abusive boyfriend Ronnie White. He only spares his infant sister. After one of the longest trials in the state's history, Michael is found guilty of first-degree murder and sent to Smith's Grove Sanitarium under the care of child psychologist Dr. Samuel Loomis. Michael initially cooperates with Loomis and his mother Deborah visits him regularly. Over the following year, Michael becomes dissociative, fixating on papier-mâché masks and withdraws from everyone around him, even his mother. When Michael kills a nurse as Deborah is leaving from one of her visits, she is unable to handle the situation and commits suicide.

For the next fifteen years, Michael continues making his masks and not speaking to anyone. Loomis, having continued to treat Michael over the years, attempts to move forward with his life and closes Michael's case. Later, Michael escapes from Smith's Grove, killing the guards and hospital staff in the process. He then kills a truck driver for his clothes and makes his way back to Haddonfield. On Halloween, Michael arrives at his now-abandoned childhood home, where he recovers the kitchen knife and Halloween mask he stored under the floorboards the night he killed his sister.

Laurie Strode and her friends Annie Brackett and Lynda Van Der Klok prepare for Halloween. Throughout the day, Laurie witnesses Michael watching her from a distance. Later that night, Lynda meets up with her boyfriend Bob Simms at Michael's abandoned home. Michael appears, murders them, and then heads to the Strode home, while Laurie is babysitting Tommy Doyle, where he murders her parents Mason and Cynthia. Dr. Loomis, having been alerted of Michael's escape, arrives in Haddonfield looking for Michael. After obtaining a handgun, Loomis attempts to warn Sheriff Lee Brackett that Michael has returned to Haddonfield. Loomis and Brackett head to the Strode home, with Brackett explaining along the way that Laurie is really Michael's baby sister, having been adopted by the Strodes following their mother's suicide. After convincing Laurie to babysit Lindsey Wallace while spending time with her boyfriend Paul, Annie is attacked by Michael after he kills Paul at the Wallace residence. Bringing Lindsey home, Laurie finds Annie badly injured on the floor but still alive, and calls for help. Michael attacks Laurie and chases her back to the Doyle residence. Loomis and Brackett hear the call over the radio and head toward the Wallace residence.

Michael kidnaps Laurie and takes her back to their old home. He tries to show Laurie that she is his sister, presenting a picture of them with their mother. Unable to understand, Laurie stabs Michael before escaping the house; Michael chases after her, but Loomis arrives and shoots him three times. Recovering, Michael recaptures Laurie and heads back to the house. Loomis intervenes, but Michael subdues him. Laurie takes the gun and runs upstairs, but Michael corners her on a balcony and charges her head-on, knocking both of them over the railing. Laurie awakens on top of an unconscious Michael. Laurie aims the gun at Michael, with Michael's hand grabbing her wrist just as the gun is fired.