WARNING: The following article contains spoilers for director Corin Hardy's The Nun, out in theaters everywhere now.
The Conjuring spinoffs have expanded upon the mythos of Warner Bros.' horror cinematic universe, but the latest installment, The Nun, sets up future events more so than the Annabelle prequels before it do. While the film's more obvious link to the larger franchise is the origin of the demon Valak that terrorizes Lorraine Warren (Vera Farmiga) throughout 2016's The Conjuring 2, The Nun has an even deeper connection that serves as the inciting incident for the entire series.
The Nun is set primarily in 1952, earlier than any other chapter in the hit Conjuring universe. Following the mysterious suicide of a nun at Cârța Monastery in Romania, the Vatican sends Father Burke (Demián Bichir) and young novitiate Sister Irene (Taissa Farmiga) to investigate after the woman's body is discovered by local villager Frenchie Theriault (Jonas Bloquet).
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Frenchie escorts the duo to the abbey, where they learn its occult history, which includes the demon Valak crossing over from Hell through a rift in the catacombs. As Burke and Irene are confronted with escalating satanic activity that begins to spread from the monastery to the surrounding area, Frenchie returns with guns blazing to save them from the evil.
The trio ventures deep in the catacombs to find an artifact containing the blood of Jesus Christ to close the rift and banish Valak back to Hell. Once inside, the demon attacks them, directly wounding Frenchie after the young farmer comes to Irene's aid when she is temporarily possessed, and Burke is injured by a ghost. Before the priest and farmer are finished off, a cleansed Irene uses the artifact to seal the rift and seemingly condemn Valak to Hell. However, while it seems they have succeeded in saving the day, the film's final twist reveals that not everyone walks away with a happy ending.
As Frenchie parts company with Burke and Irene, the farmer reveals his actual name is Maurice, which is a major clue to his role later in the franchise. While the priest and nun leave Romania for good, Maurice scratches an itch on his neck, revealing to the audience the wounds he suffered while battling Valak are actually an inverted cross marking his own secret possession by the demon.