Virginia "Ginny" Wainwright is a pretty and popular high school senior at Crawford Academy. She is one of her school's "Top Ten": an elite clique which comprises the richest, most popular and most snobbish teens at the Academy. The Top Ten meet every night at the Silent Woman Tavern, a pub near Crawford's campus.
One night, en route to the Silent Woman, Top Ten member Bernadette O'Hara is confronted by a killer whose face cannot be seen. Unable to flee, she struggles and then plays dead to catch the Killer off-guard. She fights the killer off, then runs off to get help. Instead, Bernadette finds a student whom she obviously knows well. She pleads her ordeal, only to have her throat slit when this student (whom the audience still cannot see) turns out to be the Killer.
The Top Ten are briefly concerned when Bernadette fails to show up at the Silent Woman. They promptly get over it, however; the Top Ten have a long history of playing elaborate pranks, both on each other and on the locals. Their grievance with another tavern patron inspires them to pull such a prank: they "borrow" the member's pet mouse, which they dunk into the lodger's beer, all the while pretending to apologize for their rudeness. The lodger discovers the mouse; mayhem ensues, and the Top Ten flee the scene.
En route back home, the Top Ten see a drawbridge going up and decide to play a� game of chicken: all cars in the game must make it across before the bridge is completely raised (to allow the passing of ferrys). A protesting Ginny is shoved into a car by fellow Top Ten member Ann Thomerson. Every car jumps the drawbridge save one. After the car in which Ginny is riding makes it over the bridge, Ginny has a meltdown and yells "Mother!". Ginny jumps out and bolts off toward her home nearby.
Ginny is confronted by her father about coming home after her curfew. Unbeknownst to either of them, somebody (whom the audience cannot see) has followed her home. He enters Ginny's room, steals a pair of her underwear and escapes without being seen.
Ginny shares a handful of lost, repressed memories with her on-call psychiatrist, Dr. David Faraday. She underwent an experimental medical procedure, involving surgery to restore brain tissue, after surviving a harrowing accident at a drawbridge.
As Ginny attempts to resume her normal life, her fellow Top Ten members are murdered in vicious and violent ways: Etienne is strangled when his scarf gets caught in the spokes of his motorcycle (à la� Isadora Duncan); Greg has his neck crushed while lifting weights; Alfred is gutted with a pair of garden shears...by none other than Ginny.
Mr. Wainwright leaves on a business trip. Ginny invites Steve, another member of the Top Ten, to her place for a midnight snack. She prepares shish kebabs, and feeds him, while they drink and smoke marijuana. Then Steve unsuspectingly leaves his mouth agape, and Ginny shoves the shish kebab violently down his throat.
The following morning, Ginny is taking a shower while fighting to remember everything up to that point. In flashbacks, the following is revealed.
Ginny's mother, a newly inducted socialite, invited the Top Ten to Ginny's birthday celebration four years earlier. Instead, the Top Ten went to Ann's party. Drunk and unstable, Mrs. Wainwright confronted the grounds-keeper. Ginny's mother learned that she had a reputation as the town whore; ergo, neither she nor her daughter were welcome at the Thomersons'. This led to Mrs. Wainwright attempting to drive across a bridge that was in the process of opening. With Ginny screaming, her mother finally stopped in the middle of the bridge as each side was still raising. The car fell in between the bridge halves and Mrs. Wainwright drowned in her car, although Ginny swam to safety.
Ginny realizes that she may have killed her friends after all, including Ann. With Ginny's 18th birthday steadily approaching, she struggles to get answers from Dr. Faraday; when he fails to provide any, she kills him with a fire poker.
Mr. Wainwright returns from his business trip, ready to celebrate his daughter's 18th birthday. Entering their house, he sees blood and frantically attempts to locate Ginny. Instead, Mr. Wainwright finds his late wife's grave - which recently has been robbed - and also Dr. Faraday's corpse. Entering a cottage which serves as the Wainwrights' guest quarters, he makes a ghastly discovery.
The corpses of all the murdered Top Ten members are seated around the table, which has been set to look exactly as it did four years ago. The corpse of Mrs. Wainwright is seated there as well. Then Ginny enters, carrying a large cake and singing "Happy Birthday" to herself. Already distraught, Mr. Wainwright bursts into tears when his daughter casually admits to committing the murders. Ginny then slits her father's throat with the same large knife she used to cut the cake. He never sees� another Ginny, seated at this table as the Killer's only living guest. This Ginny, the real Ginny, is sedated.
Ginny's� doppelganger� rants about having done all of this for Ginny, who then awakens to the shocking horror of all her friends having been slain by this impostor, Ann.
Ann has been embittered by the revelation of her father's affair with Ginny's mother. It turns out that both girls are half-sisters. Ann slaughtered the six main members of the clique, that never showed up for her birthday party, expressly for the purpose of framing Ginny - who suddenly breaks free, takes Ann's knife and kills her with it.
As she stands over her half-sister's corpse, a detective walks in on Ginny and the horrifying carnage that surrounds her. Immediately reaching the obvious-but-wrong conclusion, he stares at Ginny and demands, "What have you done?" Ginny can only stand there, triumphant in that she has survived her sister's murderous rampage, and yet defeated in that she must now answer for the slayings of her family and friends. The audience is then left to wonder if Ginny will be cleared of the killings or arrested for them.
We hear Ginny singing "Happy Birthday to Me" as the film ends.
- Melissa Sue Anderson� - Virginia “Ginny” Wainwright
- Glenn Ford� - Dr. David Faraday
- Lawrence Dane� - Harold “Hal” Wainwright
- Sharon Acker� - Estelle Wainwright
- Frances Hyland� - Mrs. Patterson
- Tracey E. Bregman� - Ann Thomerson
- Jack Blum� - Alfred Morris
- Matt Craven� - Steve Maxwell
- Lenore Zann� - Maggie
- David Eisner� - Rudi
- Michel-René Labelle� - Etienne Vercures
- Richard Rebiere� - Greg Hellman
- Lesleh Donaldson� - Bernadette O'Hara
- Lisa Langlois� - Amelia