Alison Parker, Cristina Raines, a fashion model haunted by childhood trauma and a history of suicide attempts, moves into a historic Brooklyn Heights brownstone. The top-floor apartment is occupied by a blind priest, Father Francis Matthew Halliran, John Carradine, who spends his days perched at his open window, watching the street below as if it were part of a private vigil. Soon after moving in, Alison begins to experience troubling physical symptoms—fainting spells, sleepless nights, and a rising sense of being watched—accompanied by eerie noises that seem to echo from the walls themselves.
As she settles into the building, she encounters a cast of peculiar neighbors who seem to harbor their own secret histories. The eccentric, elderly Charles Chazen, Burgess Meredith, projects an aura of quiet menace, while the lesbian couple Gerde Engstrom Ava Gardner and Sandra Sylvia Miles move through the shared spaces with a mix of glamour and unsettling intimacy. Alison’s attempts to make sense of the place are further unsettled when Sandra performs an private act that shatters Alison’s sense of normalcy, underscoring a building where boundaries are blurred and appearances deceive.
A bizarre birthday party for Chazen’s cat becomes a surreal microcosm of the larger mystery surrounding the brownstone, hinting at a pattern of hidden lives and hidden sins. When Alison complains to the rental agent Miss Logan, played by Deborah Raffin, she’s told that the building’s population is deceptively small—only Halliran and a lone tenant—throwing doubt on Alison’s perception of who actually lives there and what lurks behind the facade of normalcy.
Michael Lerman, Alison’s lawyer boyfriend, turns to his corrupt detective friend James Brenner, a troubled link in a chain of financial and moral intrigue, hoping to uncover the truth behind the strange happenings in the building. Brenner’s eventual actions pull Alison deeper into a perilous conspiracy, and a night that begins with routine inspection ends with a violent confrontation in which Alison is forced to confront the possibility that her own family history—her father’s death, the weight of unresolved traumas, and the moral compromises of those around her—may be more entangled with the present danger than she could have imagined.
The investigation takes a nightmarish turn when Brenner visits the property and Alison, confronted by a chilling apparition—her deceased father—must defend herself by stabbing him, a moment that lands her in the hospital with a nervous breakdown. The case draws the attention of two police detectives, Gatz and Rizzo, whose presence hints at a wider conspiracy—one that threads through the relationships within the building and points toward Michael’s possible involvement in violence that mirrors the darker impulses of those around him. Clues begin to accumulate: Brenner’s corpse is found, and the court of rumors suggests that Alison may have had a hand in his death, entwining her fate with those of the people she once trusted.
Complicating matters is Alison’s growing ability to read Latin words that others cannot, a sign that she may be part of something beyond ordinary perception. She visits a Catholic church and confesses sins including her adulterous affair with Michael to Monsignor Franchino, José Ferrer. The confession scene deepens the sense that the brownstone operates as a gateway to a hidden order of forces that transcend conventional morality. Michael’s later actions—his break-in at the Diocesan office and his discovery of Halliran’s file—reveal a chilling lineage: Halliran is revealed to be a sentinel figure, part of a chain of priests and nuns who have, for generations, sought to seal or seal off the entry to Hell, using those who follow them as vessels for a larger cosmic mechanism. Alison is disclosed as the latest link in this lineage, supposedly destined to take on a ceremonial role when the time comes.
As the truth unfolds, Halliran’s struggle with demonic forces intensifies, and Michael’s death at the hands of Franchino underscores the gravity of the conflict. In a climactic reckoning, Alison is faced with a choice: join Michael in Hell or accept her own role as the new Sentinel, a duty that could save her soul. With Halliran’s fraught exertions drawing the demons toward the surface, Alison ultimately takes up the cross and embraces her destiny, resisting the temptations offered by Chazen and the infernal minions. The Sentinel’s victory is not a triumph of force but of vocation, with Alison choosing to carry the burden rather than surrender to the darkness.
In the aftermath, the brownstone is razed and replaced by a modern apartment complex, a stark symbol of how the past can be cleared away, yet the building’s legacy lingers in subtle ways. Miss Logan later shows a prospective tenant a new unit, describing two distinct neighbors—the violin player and a reclusive nun—hinting that the cycle could begin anew for other inhabitants. The film closes with Alison, now blind and clad in a nun’s habit, sitting near the top window and gazing out, a quiet, resolute figure who embodies the tension between memory, sacrifice, and the possibility of redemption within a world where the thresholds between life and the beyond remain perilously thin.
