Michael Kovak, portrayed by Colin O'Donoghue, grapples with a profound disillusionment stemming from his relationship with his father, who operates a mortuary. Seeking to escape this legacy and secure a free college education, he enrolls in a seminary, fully intending to renounce his vows upon graduation. Fast forward four years, Michael stands on the brink of ordination, but immediately afterward, he writes a resignation letter to his superior, Father Matthew, played by Toby Jones. This letter is rooted in his deep-seated crisis of faith. In an attempt to dissuade Michael from this hurried decision, Father Matthew attempts to catch up with him, but fate intervenes when he trips over a curb, inadvertently causing a biker to veer toward an oncoming vehicle.
In a twist of irony, it’s Michael whom the young woman, mistaking him for a priest in his clerical attire, seeks out for absolution. Despite his skepticism, he cannot turn her away; thus, he comforts her and performs the act of absolving her sins. Witnessing Michael's calm demeanor in this moment, Father Matthew insists that Michael has a calling to the priesthood, regardless of his own feelings about it. Soon after, Father Matthew presents Michael with a compelling opportunity: a chance to travel to Rome for an exorcism class. Michael, now faced with the daunting prospect of a $100,000 student loan should he leave seminary, reluctantly agrees, though he reserves the right to withdraw post-class if he wishes.
During his time in Rome, he crosses paths with the intriguing Angelina, played by Alice Braga. Unbeknownst to him initially, she is a reporter there to cover the exorcism course for a feature article. Soon, Father Xavier, portrayed by Ciarán Hinds, recognizes Michael's skepticism about faith and encourages him to seek counsel from the esteemed Father Lucas, played by Anthony Hopkins, a celebrated Welsh Jesuit exorcist. Intrigued yet apprehensive, Michael accepts this advice and meets Father Lucas at his residence, where he is introduced to one of Lucas's patients: a troubled sixteen-year-old girl grappling with demonic possession following a horrific trauma inflicted by her father.
Despite witnessing several unsettling phenomena—such as the girl expelling long nails and speaking in tongues—Michael remains resolute in his skepticism. His introspections are further complicated when Elena asks him to share insights from Father Lucas, yet Michael feels torn and declines her request. As the girl's plight intensifies, Father Lucas and Michael decide to transfer her to a hospital for urgent intervention. Here, Michael witnesses another exorcism orchestrated by Father Lucas while he, in an act of integrity, chooses to withdraw from the event afterward. Tragically, the night culminates in the death of both the girl and her unborn child, leaving Father Lucas despondent and perceiving himself as a failure.
The situation takes a dark turn when Father Lucas begins to exhibit signs of demonization himself. In a moment of isolation, he sits in the rain outside his home until Michael and Angelina find him. Aware of his affliction, Father Lucas beseeches Michael to locate Father Xavier to facilitate his exorcism. However, when they learn Father Xavier is unreachable for three days, Michael makes a pivotal choice: he decides to conduct the exorcism solo, with Angelina at his side. After a fierce confrontation with the demon—who reveals itself to be named Baal—Michael triumphantly regains his lost faith and successfully expels the demon from Father Lucas’s body.
The film reaches an emotional crescendo as Michael prevails and subsequently returns to the United States, now transformed. In its closing moments, we find him donning the robes of Father Michael Kovak, stepping into a confessional to hear a girl’s confession. This marks his journey from skepticism to spiritual enlightenment, solidifying his commitment and newfound vocation as a priest.
