In 1952 Romania, two nuns living at the Cârța Monastery are attacked by an unseen presence while searching for an “artifact”. The surviving nun, Sister Victoria, flees from the attacker and jumps out of a window, hanging herself, as the attacker, a demonic entity called Valak appears outside her room. Her body is discovered the next morning by Frenchie, a man who lives in the nearby village and who is tasked with transporting supplies to the nuns despite never actually seeing them.
The Vatican learns of the death and dispatches troubled priest Father Burke to investigate along with young novitiate Sister Irene. The pair travels to Romania and meets with Frenchie who leads them to the abbey. At the abbey they discover that Sister Victoria’s body has inexplicably moved from where Frenchie originally moved it, fresh blood appears where she was initially found and a strange key on her body. Entering the chapel outside the abbey, they find themselves unable to enter the actual abbey and encounter the abbess. She tells them that the nuns are currently having a vow of silence for the night and they can enter tomorrow. Irene and Burke send Frenchie away while they stay in guest rooms. Frenchie is attacked by a possessed nun corpse as he heads to the village but manages to escape. Irene mentions how she has various visions including that of a nun. Additionally, Burke reveals that a boy he exorcised died during the exorcism and he has been grieving ever since. Valak terrorizes the pair that night and Burke is rescued by Irene after being trapped in a coffin. In the coffin are several books about the occult.
The next day, Irene and Burke go to enter the abbey but as it is cloistered, only Irene can enter. She meets some of the other nuns and learns that they are praying constantly, swapping in shifts to keep evil at bay. One of the nuns, Sister Oana, reveals that the abbey was built during the Dark Ages by a duke obsessed with the occult and satanic and who summoned Valak via a rift he opened in the catacombs. Troops loyal to the Vatican stormed the church, killing the duke and sealing the rift with an artifact that contains the “blood of Jesus Christ” before Valak could fully emerge. However, the abbey was hit by bombs during WWII and the rift was opened again, unleashing Valak who has taken the form of a nun and whom several nuns have spotted at night. Meanwhile, in the chapel, Burke identifies the entity as Valak after reading the books in the coffin and discovers the abbess’s body is being controlled by demonic forces who shift into the boy who died during the exorcism.
In the village, Frenchie discovers that the evil from the abbey is seeping into the village, after learning of the suicide of a young girl, and decides to head back to the abbey to try and save Irene and Burke. Irene is attacked by Valak and experiences more visions that night. She enters the main part of the abbey where several nuns start to pray to fend off Valak. The group is attacked, suffering large casualties and a demonic force carves a pentagram into Irene’s skin. Hearing the chaos, Burke tries to enter the abbey to save Irene but is attacked by a possessed nun corpse. He is saved by a shotgun-wielding Frenchie and the pair enter the abbey to rescue Irene. Upon reaching Irene, the group discovers that none of the nuns were real and they were all visions from Irene. Sister Victoria was the last nun alive and had actually hung herself to stop Valak from possessing her body and spreading its evil elsewhere.
Theorizing that if they seal the damaged rift with the blood then they can stop Valak, the trio enter the catacombs and retrieve the blood vial with the key Sister Victoria had before searching for the rift. The group is attacked and separated by Valak and the ghosts of the dead nuns. Irene is lured into a pentagram and possessed by Valak. Frenchie uses some of the blood to free her. Valak emerges, incapacitating Frenchie and throwing Irene into the room with the rift which is now flooded. Burke is wounded by the ghost of the boy who died as Valak starts to drown Irene. As Valak inspects Irene’s body, she spits the blood at the demon, banishing it before using the blood to seal the rift. Frenchie manages to pull Irene out of the water and the trio celebrates their victory. Frenchie reveals his real name is Maurice to Irene and the group leave the abbey. However, it is shown that Maurice is actually possessed by part of Valak via injuries he sustained during the fight.
In 1971, Carolyn Perron watches footage of the Warrens attempting to exorcise Maurice at a seminar. Maurice touches Lorraine giving her visions of Ed dying, which starts the events of The Warrens investigating the Perron household haunting, as well as their encounter with Valak itself.
Starring: Demián Bichir, Taissa Farmiga, Jonas Bloquet