In the haunted shadow of New Orleans, a chilling battle between faith and an ancient evil unfolds. While praying in St. Agnes church, Father Dennis, Ruben Rabasa, is confronted by a demon that takes the shape of a seductive woman and tears his throat, ending his life in a brutal, unsettling moment. Years later, a similar nightmare visits the living when Father Michael, Ben Cross, is at a New Orleans hotel to help Claude, a man threatening to jump from the top floor. When Michael offers Claude a cigarette, he’s inexplicably pulled out the window and plummets, yet survives the fall unscathed—an event that will crowbar open a door to forces beyond reason.
This miraculous rescue leads to Michael’s appointment to the St. Agnes parish by Archbishop Mosely, Hal Holbrook, a parish that had been shut after Dennis’s unsolved murder. As Michael settles into the rectory, Lieutenant Stern, Ned Beatty, informs him that another priest was murdered there in the past. In Dennis’s journal, Michael discovers a name that will draw him deeper into the club’s dark underbelly: Millie, a waitress at Threshold, a local black-magic performance club. When Michael seeks her out, Millie proves evasive, her memories foggy and her truth elusive. She later approaches Michael, claiming she saw Dennis for confession before his death and admitting that she has bound her soul to Luke, the club’s enigmatic owner, whom she insists is the Devil incarnate. Luke himself visits Michael, insisting that the club’s shows are mere gimmicks and that he does not truly believe in dark powers; yet he confesses to experiencing supernatural disturbances and pleads for help. Michael agrees to spend an evening in Luke’s apartment, where he bears witness to furious poltergeist activity that shatters the boundary between the natural and the supernatural.
When Michael reports his experiences to Archbishop Mosely, he is told that Dennis also met Millie and Luke in a similar manner before his murder. The aging demonologist Father Silva, Trevor Howard, counsels that Michael has been “chosen” to confront the devil, though Michael remains wary of such prophecies. Millie is later incarcerated after an attempt on Luke’s life, and Michael visits her. In a moment of fevered delirium, she claims Luke tried to rape her and that Dennis has been speaking to her from beyond the grave. That night, Michael experiences a nightmare of the demon and even receives a phone call from Dennis, who declares that he is “waiting for him in hell.” Millie soon arrives at the rectory again, seeking shelter.
While cleaning the church with Teresa, Lari White, Millie becomes absorbed by a statue of the Immaculate Heart of Mary. Stern continues to warn Mosely that Michael’s life may be in danger, but Mosely remains confident that the priest is safe for the moment. Millie’s search leads her to a book about the Unholy, a demon bent on corrupting and consuming pure souls. To shield herself from danger, she propositions Michael to take her virginity, a request he refuses. Suspecting Luke of planting the book, Michael confronts him, but Luke denies it.
The next day brings a brutal turn of events: Luke’s body hangs above the church altar in the sign of the Cross of Saint Peter, while Claude sits in a pew and begs Michael’s forgiveness for his fall. Claude then begins to bleed from his eyes and mouth and bursts into flames at the foot of the Immaculate Heart of Mary; Luke’s corpse also ignites. In consultation with Mosely and Silva, Michael learns that the Unholy will manifest to him between Ash Wednesday and Easter, attempting to tempt and destroy him. In the church, the Unholy appears first as the seductive woman, testing Michael’s resolve, and then reveals its monstrous true form as two mutant beings crucify him. Millie returns to the church and confronts the creature, but Michael calls on God for strength, condemning the Unholy to hell. He collapses, and when he wakes, he is blind. As Millie leads him out, the Immaculate Heart statue weeps tears of blood, and the battle between faith and darkness leaves its indelible mark on them both.
