A group of seven senior students — Jackie [Mollie O'Mara], Elizabeth [Sharon Christopher], Kate [Colleen Harrity], Karen [Beth O'Malley], Susan [Karen Krevitz], Adelle [Marcia Hinton], and Rosemary [Monica Antonucci] — at the all-girls Catholic Trinity College are sent to spend four days cataloging a vast art collection in the now-empty Welles mansion, a place long rumored to be haunted by a vengeful female ghost. The project is overseen by the elderly Sister Urban [Vera Gallagher], who is surprised upon arrival to be greeted by Dr. Robert Fisher [Tony Manzo], a man presenting himself as a prospective buyer of the home.
On the first day inside, Jackie discovers a diary dating back to the 1930s belonging to Jennifer Welles, [Mollie O'Mara] a Trinity College alumnus and the niece of Tyler Welles, the mansion’s original owner. In Jennifer’s writing, she mentions Sister Urban and reveals a desire to become a nun. When Jackie brings up the name during dinner, Sister Urban explains that the orphaned Jennifer was killed at the mansion in an accident. That night, the group—aside from Jackie and Adelle—proposes a seance to contact Jennifer’s spirit, triggering what seems like poltergeist activity. After the others drift to sleep, Jackie and Elizabeth come upon a large portrait of Jennifer in the parlor that eerily resembles Jackie herself. Unable to sleep, Jackie pores over Jennifer’s diary and uncovers a dark history: Jennifer endured sexual advances from her uncle Tyler, and the relationship grew into an incestuous bond.
The following day, Jackie and Elizabeth attempt to hide the portrait from the others while cataloging items. Sister Urban grows increasingly ill and spends the remainder of the night bedridden. In the meantime, Rosemary is murdered with a meat cleaver by an unseen assailant while riding in a dumbwaiter. The others assume she’s pranking them when she fails to meet them for dinner; Karen heads to the basement to look for her and instead uncovers Rosemary’s lifeless body stuffed inside the dumbwaiter. Shortly after, Kate is dragged into a pond outside by a rotting, decomposed hand and is killed as well.
Soon after, Paul, Jackie’s boyfriend, and his friend Bruce arrive at the mansion, startling Susan. While Paul locates Jackie, Bruce is run over and killed by Paul’s car outside. Back inside, Sister Urban’s illness deepens, and Elizabeth and Susan stand vigil at her bedside, growing increasingly worried. Susan is lured into the attic, locked inside, and electrocuted to death, her body left to burn in a sudden incineration. Jackie and Paul begin a frantic search for Adelle and Bruce, and outside, Paul is stabbed to death with a pitchfork by the killer, who is posed as a sculpture wearing a babydoll mask.
Desperation mounts as Jackie, unable to locate anyone, finds Sister Urban in the hallway in a feverish, confused state. After tucking Sister Urban back to bed, she ventures to the basement, where she discovers all of her classmates’ corpses—save Elizabeth, who has been kidnapped and remains alive—seated in chairs before a ceremonial altar. There, she confronts Dr. Robert Fisher, who is in fact Tyler Welles, intent on marrying Jackie because he believes her to be the reincarnation of his dead niece. In the meantime, Sister Urban manages to summon Jennifer’s spirit, which possesses Jackie and enables a calculated act of vengeance against the monstrous uncle Tyler: she gouges out his eyeballs, exacting justice for Jennifer’s decades-old murder. Jackie, Elizabeth, and Sister Urban manage to flee the house in an ambulance. As they drive away, an apparition of Jennifer looks down from an upstairs window, a lingering reminder of the mansion’s tragic legacy.
