Hello Mary Lou: Prom Night 2 is a 1987 film, the second installment in the Prom Night saga. It introduced the vengeful female ghost named Mary Lou Maloney, who returned in 1989 film Prom Night 3: The Last Kiss.
In 1957, seventeen year-old Mary Lou Maloney (Lisa Schrage) enters a church, where she confesses her sins to the priest (Jay Smith, claiming to have disobeyed her parents, used the Lord's name in vain and had sinful relations with various boys. The pastor tells her that "these are great sins and she should prepare herself for the consequences." Before leaving, Mary Lou tells the priest that she loved every minute of it and leaves her phone number in the confession booth along with a written message: "For a good time call Mary Lou."
Later, at the 1957 prom at Hamilton High School, Mary Lou is attending with rich Billy Nordham who gives her a ring with her initials on it. Shortly after receiving Billy's ring, Mary Lou sends him off to get punch while she sneaks backstage with Buddy Cooper, where the two are found making out by Billy. Storming off after Mary Lou claims she used him, Billy, while in the washroom, overhears two boys preparing a stink bomb and, when the boys abandon the bomb in the trash due to a teacher approaching, Billy grabs it. When Mary Lou is crowned prom queen, Billy, having sneak up onto the catwalk, drops the bomb on her before she is crowned. To the horror of Billy and everyone in attendance, the fuse of the bomb ignites Mary Lou's dress and she dies after going up in flames, but not before seeing that Billy is the one who killed her.
Thirty years later, high school student named Vicki Carpenter (Wendy Lyon) goes looking for a prom dress in the school prop room after being denied a new dress by her overly religious mother. While searching, Vicki finds an old trunk containing Mary Lou's prom queen accessories (her cape, sash, ring and crown) and takes them, releasing Mary Lou's hell-bound spirit. After Vicki leaves Mary Lou's clothes in the art room after school, Vicki's friend named Jess Browning (Beth Gondek) finds them and, after wedging a jewel out of the crown, is attacked by an unseen force and hung from a light by Mary Lou's cape. Jess's death, however, is deemed a suicide caused by her despair over her recent discovery that she was pregnant.
After Jess's death, Vicki finds herself plagued by nightmarish hallucinations caused by Mary Lou and she confides in Buddy Cooper (Richard Monette), who is now a priest and, after hearing Vicki's stories, believes Mary Lou may be back from dead. Going to Mary Lou's grave, where his bible bursts into flames, Buddy afterwards tries to warn Billy (now played by Michael Ironside), who is now the principal of Hamilton High and the father of Vicki's boyfriend named Craig (Louis Ferreira); Buddy's warnings fall on deaf ears, with Billy refusing to believe that Mary Lou has returned from the dead to reclaim her title as prom queen and to seek revenge on those who wronged her for no reason
During a detention caused by her slapping her rival named Kelly Hennenlotter (Terri Hawkes), who she envisioned was Mary Lou, Vicki is dragged into the classroom chalkboard, which turns into a liquid. Taking control of Vicki's body, Mary Lou visits Buddy at the church and, revealing her identity to him, kills him in cold blood by stabbing him by the face with a miniature crucifix. Disposing of Buddy's corpse, Mary Lou makes over Vicki's body, her new mannerisms and style of dress arousing the concern of Vicki's friend named Monica Waters. After confronting Mary Lou in the girls locker room, Monica is killed and slaughtered by Mary Lou when, after hiding from Mary Lou in a locker, she is crushed to death when Mary Lou makes the locker collapse in on her, causing Monica's brain to spurt out through the locker ventilation slits.
After Monica's murder, Mary Lou seduces Craig and lures him away under the pretense of having sex, only to knock him out and afterward confront and taunt Billy, revealing her identity to him. Finding the injured Craig, Billy takes him home and knocks him back out when Craig tries to go after Mary Lou. With Craig knocked out, Billy digs up Mary Lou's grave and finds Buddy's corpse in the coffin, which prompts him to acquire a gun and head to the prom. At Vicki's house, Mary Lou seduces Vicki's father named Walt and is found kissing him by mother named Virginia, who tries to stop Mary Lou (in Vicki's body) from leaving for the prom, only to be thrown and smashed through the front door.
Arriving at the prom, Mary Lou enjoys the festivities while Kelly , in order to become prom queen, fellates tally counter Joshua as a bribe. When Josh changes the outcome of the votes to make Kelly winner instead of Vicki, Mary Lou, sensing this, electrocutes Joshua through his computer and changes the outcome back. When she is crowned prom queen, Mary Lou goes up on stage, but is shot moments before getting her crown by Billy. Arriving after the shooting, Craig, reaching what appears to be the dying Vicki, is knocked back when Vicki changes into a charred corpse and then into Mary Lou. In the havoc caused by Mary Lou's appearance, Kelly is killed by a falling light fixture and Craig is chased into the school prop room by Mary Lou, who opens a vortex to the underworld that begins to suck Craig in. Before Craig is pulled through the gateway, Billy arrives and places the crown on Mary Lou, apparently appeasing her spirit/ghost, which vanishes, thus releasing and freeing Vicki.
With Mary Lou gone, Vicki and Craig leave with Billy, getting into his car. When Billy turns on the radio, Mary Lou's signature song "Hello Mary Lou" plays and Billy, revealing he is wearing Mary Lou's ring (apparently as revenge for killing her in the first place thirty years ago, Mary Lou had possessed him by making him her new host), drives off with the terrified Vicki and Craig.
- Michael Ironside as Principal Billy "Bill" Nordham
- Wendy Lyon as Vicki Carpenter
- Louis Ferreira as Craig Nordham
- Richard Monette as Father Cooper
- Lisa Schrage as Mary Lou Maloney
- Terri Hawkes as Kelly Hennelotter
- Wendell Smith as Walt Carpenter
- Judy Mahbey as Virginia Carpenter
- Beverley Hendry as Monica Waters
- Brock Simpson as Josh
- Beth Gondek as Jess Browning
The film made a little over $2,800,000 at the U.S. box office. The film was more of a success on home video. It currently has an approval rating of 38% on review aggregator website Rotten Tomatoes, based on 8 reviews.
As a promotion for the 2008 remake of Prom Night, MGM Home Entertainment (distributed by 20th Century Fox Home Entertainment) released a new widescreen DVD of Hello Mary Lou on April 1, 2008. The film had earlier been released in Canada in 2003 as a full-screen DVD from Alliance Atlantis.