Hello Mary Lou: Prom Night II is a 1987 Canadian supernatural slasher film directed by Bruce Pittman, and starring Michael Ironside, Wendy Lyon, Louis Ferreira, and Lisa Schrage. It follows a high school student who becomes possessed by Mary Lou Maloney, a student who died at her high school prom in 1957. A sequel to the slasher film Prom Night (1980), it was originally intended to be a standalone film titled The Haunting of Hamilton High, but was retitled in order to capitalize on the success of the original Prom Night. The only story connection between the two films is that they are set at the same high school. However, both films were executive produced by Peter R. Simpson.

Plot

In 1957, 17-year-old Mary Lou Maloney confessed her various sins to a priest en route to her senior prom. Before leaving, she defiantly tells the priest that she loved every minute of her sinning and gives him her phone number. She goes to the Hamilton High School prom with wealthy but unpopular Billy Nordham, who gives her a ring with her initials. Shortly after receiving Billy's ring, Mary Lou sends him off to get refreshments before sneaking backstage to make out with Buddy Cooper. Billy catches them in the act, but Mary Lou leaves him for Buddy. She then dumps her drink on his jacket. While cleaning up in the bathroom, Billy overhears 2 boys preparing a stink bomb. The boys abandon the bomb in the trash due to the principal approach, but once he leaves, Billy grabs it. Mary Lou is announced as prom queen and Billy, having snuck up onto the catwalk, drops the bomb on stage before she is crowned. To the horror of Billy and everyone in attendance, the flames from the bomb ignited her dress. Due to their panic, no one attempts to save her and she burns to death. But not before looking up and seeing that Billy is the one who’s responsible.