Set immediately after the events of the previous film, Cameron Elam finds a wounded Deputy Frank Hawkins while walking home from a Halloween party. Hawkins regrets withholding serial killer Michael Myers’ execution and resolves to kill him himself that night. In a flashback to 1978 (just after the end of the original), Hawkins accidentally shoots and kills his partner in pursuit of Michael before preventing Michael’s psychiatrist Dr. Sam Loomis from executing him in front of Michael’s childhood home.
During present day, on October 31, 2018, Tommy Doyle celebrates the 40th year anniversary of Michael’s imprisonment with longtime friends Marion Chambers, Lindsey Wallace, and Cameron’s dad, Lonnie Elam. Meanwhile, after their confrontation with Michael, Laurie Strode, her daughter Karen, and her granddaughter Allyson are horrified when a group of firefighters arrive at the burning Strode residence, accidentally freeing Michael from the basement. Using their tools, Michael singlehandedly murders the firefighters before driving back to Haddonfield.
Karen and Allyson submit Laurie to emergency surgery while Michael kills an elderly couple in their home. An emergency alert informs Tommy, Marion, Lindsey, and Lonnie of Michael’s escape before bar patron Vanessa supposedly encounters Michael in the backseat of her car. Tommy and the others confront Michael as the car drives away and crashes; the driver leaves unnoticed by the crowd. En route to collect Cameron, Tommy forms a mob full of vengeful Haddonfield citizens to hunt down Michael before he can hurt anyone else.