Halloween 4 follows one long night, from Michael Myers waking in an ambulance to a mob shooting him into a mine shaft. On Halloween eve in 1988, Michael is being transferred to a new sanitarium when he hears that he has a living niece. He wakes from his coma, kills the ambulance crew and makes for Haddonfield.
Jamie Lloyd, who lives with the Carruthers family, is haunted by dreams of him, and her foster sister Rachel cancels a date to mind her on Halloween night. Dr. Loomis learns Michael has escaped and heads for Haddonfield. He fights Michael at a gas station, but Michael gets away in a tow truck and Loomis has to continue on foot.
Jamie goes trick or treating in a clown costume, and Michael later breaks into her home and learns who she is. He then cuts the town's power and kills most of the local police, and an angry mob of townspeople forms. Sheriff Meeker and Loomis take the girls to the sheriff's house, but Michael follows and kills several people there, so the girls flee across the rooftops.
Michael chases Jamie and Loomis to the school, and Rachel helps drive him off. He then hides under the truck carrying the girls out of town and kills several members of the mob. Rachel throws him off the truck and runs him down, and he is shot repeatedly before he falls into an abandoned mine.
Back at the Carruthers house, Jamie is found in her clown costume holding bloody scissors, and Loomis realizes that Michael's evil has passed to her. The next section, Halloween 4 ending explained, covers what that final image means and how the following film uses it.