The focus of Halloween II is on the connection between Michael Myers and his younger sister Laurie Strode. It was intended to be more violent and realistic than the previous film.
Halloween II was rated R by the Motion Picture Association of America for continuous terror and brutal violence, some particularly disturbing images, some crude sexual content, nudity and bad language. The movie was a moderate box office success. It was made on a budget of $15,000,000 and earned over $39,000,000. However, it received largely negative reviews.
So far, there has been no sequel to this movie.
In a flashback, Deborah Myers, Michael Myers' mother, visits her son at the Smith's Grove-Warren County Sanitarium. She gives him a white horse statuette as a present. This prompts Michael to tell his mother that he has had a dream in which her ghost, dressed in white, led a white horse through the corridors of the sanitarium, came to her son and told him she was bringing him home.
The action then moves forward to the point where the previous movie ended. having just shot Michael Myers, Laurie Strode is found wandering around, covered in blood and in a state of shock. She is taken to the emergency room by Sherriff Brackett. The sheriff's daughter, Annie Brackett, and Michael's former psychologist, Dr. Samuel Loomis, have both been attacked by Michael but are still alive and are taken to hospital. Michael is believed to be dead and his body is placed in another ambulance. However, when the ambulance driver has an accident, Michael suddenly springs to life, escapes from the ambulance and walks towards a vision of his mother and a white horse.
Michael arrives at the hospital that Laurie has gone to for treatment, murdering everyone who stands in his way. Laurie finds herself trapped in a small security guard's office outside the main hospital building. Michael breaks through the walls and is about to kill Laurie when she wakes up. It is one year later. Laurie, following the murder of her parents, is now living with the Brackett family. She has been having recurring nightmares about the events of the previous year and is undergoing therapy. Michael Myers is believed to be dead but his body has not been found.
Michael begins to see visions of his mother and himself as a boy. In the visions he is told that Halloween is coming and it is time to bring Laurie home. Michael sets off for Haddonfield, in search of his sister. Laurie also begins to have hallucinations in which she sees Deborah Myers and the young Michael Myers in a clown costume. She also sees herself carrying out the murders that Michael Myers committed.
Dr. Loomis writes a book about his experiences with Michael Myers. He goes on tour to promote it and faces criticism that he is exploiting the murder victims and that he is responsible for their deaths. When the book is published, Laurie finally learns that she was born Angel Myers and that she is Michael Myers' sister.
Michael arrives in Haddonfield and murders some of Laurie's friends. He goes to the Bracketts' house and attacks Annie. Laurie returns and finds her friend wounded. Michael appears and she runs out of the house. She is able to flag down a passing car but, before she can go anywhere, Michael kills the driver and flips over the car with Laurie still inside it. Laurie is knocked unconscious.
Laurie comes round in an abandoned shed that Michael has been using as a hideout. She sees a vision of Deborah Myers and a young Michael, urging her to say, "I love you, mommy". Police surround the shed and Dr. Loomis enters to try to reason with Michael. Laurie tells him that she is being held down by the child Michael. Dr. Loomis has to tell her that nobody is holding her down. In a vision, Michael's mother tells him that it is time to go home. He moves in front of the shed's window and stabs Dr. Loomis. He is shot and falls onto the spikes of some farming equipment.
Laurie tells Michael that she loves him before stabbing him. She walks out of the shed wearing Michael's mask. As she takes the mask off, the scene changes to Laurie in isolation in a psychiatric hospital, grinning at a vision of Deborah Myers and a white horse.