Maya Larkin, Winona Ryder, is a devout Roman Catholic and a dedicated schoolteacher for a New York City diocese. She joins Father Lareaux, Father Jeremy, and John Townsend on a tense mission to a psychiatric clinic where they attempt to exorcise Henry Birdson, a man plagued by epileptic seizures and a disturbing compulsion to scribble a cryptic sequence of numbers. The ritual proves fruitless: Henry slips into a coma, and Father Lareaux appears weakened by the strain. In a bid to unravel the mystery, Maya discreetly smuggles out Henry’s notes and, using polyalphabetic substitution, deciphers the enigmatic digits to reveal the name Peter Kelson Ben Chaplin.
Across town, Peter Kelson—an author who covers serial killers, narcissism, and parapsychology—meets with his family during a quiet dinner. He recounts a recurring dream in which he is reading a book whose cover bears the letters “XES.” A later clue from a priest clarifies that this is the Greek number חез (χεζ), whose numerical value points to a chilling omen: the devil’s incarnation will cross paths with a man on the precise moment of his 33rd birthday.
As Maya digs deeper, she becomes convinced that Peter is the living embodiment of evil. She confronts him with a unsettling profile: a unique blood type, a stubborn disbelief in pure evil, and the startling fact that his infant baptism was performed not by clergy, but by a family member. Determined to prevent catastrophe, she persuades Peter to join in an exorcism, while simultaneously guiding him to look for a pentagram hidden under his bed and handing him the recording of Henry’s exorcism—only to find the tape in his apartment eerily silent. When Peter plays it, the supposed torment is not his alone: Henry’s screams echo from a neighboring apartment, and that resident is later found to have killed herself.
Peter soon shares the pentagram with his girlfriend Claire after discovering it in the false ceiling of the adjacent unit. Claire responds with fear and fury, pulling a gun and threatening Maya, insisting that Peter is being deceived. A violent struggle ensues, and a shot is fired that inadvertently kills Claire.
To pull off the exorcism that could save Peter, Maya and their circle turn to Father Lareaux. Yet Lareaux, tainted by the earlier exorcism, has themselves become possessed, and the exorcism is redirected to him—yielding his death. On his deathbed, Lareaux urges Peter and Maya to seek Peter’s uncle, Father James, who is conducting mass in a church populated by Peter’s extended family. The confrontation escalates as Peter shoots his uncle and two other relatives before fleeing with Maya.
The chase ends beneath a blocked bridge, where Peter, cornered by his fate, passes the gun to Maya. As the digital clock in their vehicle flips to 6:66 a.m., Peter completes his transformation into the human incarnation of Satan, and Maya, in a final act, shoots him dead.
