On Halloween 1978 in Haddonfield, Illinois, a ten-year-old boy, Michael Myers, murders his school bully Wesley Rhoades, his alcoholic stepfather Ronnie White, his abusive older sister Judith Myers and her boyfriend Steven Haley, only sparing his baby sister Boo. After one of the longest trials in the state's history, Michael is found guilty of first-degree murder and sentenced to Smith's Grove Sanitarium under the care of child psychologist Dr. Samuel Loomis.
Michael initially cooperates with Loomis and his mother, Deborah Myers, who he loves dearly, as she visits him regularly. Over the following years, Michael begins to dissociate and fixates on his papier-mâché masks, withdrawing from the people around him, even his mother. When Michael ends up killing 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 people. 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, takes his clothes and makes his way back to his hometown of Haddonfield.
On the day of 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 family.
Laurie Strode(/actor/scout-taylor-compton) 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 later appears, murders them, and then heads to the Strode home.
There, while Laurie is babysitting Tommy Doyle, he murders her parents, Mason and Cynthia. Dr. Loomis, having been alerted of Michael's escape, drives to Haddonfield in search for Michael. After obtaining a handgun, Loomis attempts to warn Sheriff Leigh Brackett about Michael.
Loomis and Brackett rush over to the Strode home, with Brackett explaining to him that Laurie is really Michael's baby sister, having been adopted by the Strodes after their late 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, chasing her down the street and 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, as he tries to show Laurie that she is his sister, presenting a picture of both of them together. Unable to understand, Laurie stabs Michael in the neck 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 by gouging at his eyes. Laurie takes the gun and runs upstairs where she hides inside of the walls. Michael corners her on a balcony and charges at her head-on, knocking both of them over the side of the railing. Laurie awakens on top of an unconscious Michael and aims the gun at his face, with Michael's hand grabbing her wrist just as the gun is fired. Police sirens are heard in the distance.
