Valak (Bonnie Aarons) is a Catholic desecration, a habit-wearing, shape-shifting demon first introduced haunting Vera Farmiga's clairvoyant Lorraine Warren in 2016's '70s-set "The Conjuring 2" and briefly appearing in 2017's 1955-set prequel "Annabelle: Creation." In "The Nun," the next addition to "The Conjuring Universe," the clock spins back further to 1952 as this malevolent figure—described as "the defiler, the profane, the marquis of snakes"—glides toward the story's forefront. The film, directed by Corin Hardy (2015's "The Hallow") and written by Gary Dauberman (2017's "Annabelle: Creation"), exudes high production values and heavy-duty fog machines working overtime. What it lacks is a satisfying, soundly conceived narrative; when all is said and done, this is but 96 minutes of characters meandering around shadowy locations as they wait for abominable nightmare fodder to leap out. As an origin story for Valak, little is learned which wasn't already established and connections to past installments in the series are arbitrary, at best.

When Sister Victoria (Charlotte Hope) is found hanging outside the Abbey of St. Carta, Father Burke (Demián Bichir) is called upon by the Vatican to investigate what appears to be a tragic suicide. Accompanying him on his journey to the monastery, located in the mountains of Romania, are Sister Irene (Taissa Farmiga), a novitiate who has yet to take her vows, and Frenchie (Jonas Bloquet), the young man who discovered the body. Almost immediately, things do not appear quite right. The corpse, left lying down in the icehouse, is found upward in a sitting position. A radio (playing Jo Stafford's pop ballad "You Belong to Me") turns on by itself. There are unexplained sightings of a ghastly nun, and Father Burke is plagued by glimpses of a possessed boy who died years ago following an exorcism. As Burke and Irene begin to research the abbey's sordid history, they find what could be a stronger connection to Hell than to godliness.

"The Nun" is gripping during its first half, then less so once scenes grow repetitive and the machinations of the slim plot begin to creak. In getting to the bottom of Sister Victoria's demise, Father Burke and Sister Irene take the bulk of the film to reach the conclusion blatantly explained to the audience in the prologue. Waiting for protagonists to catch up to what the viewer already knows does not exactly an engaging mystery make. Director Corin Hardy is most successful in moments of bewitching misdirection, spook-centric set-pieces where the threat arrives from an angle least expected. A sequence involving Frenchie following a darkened figure in a habit through the nighttime forest is solidly suspenseful, as is another relatively early sequence involving bells in a cemetery. By and large, however, the situations found within are overly familiar and simply not very frightening. More subtlety and dread, less demonic faces jumping out of the darkness could go a long way toward avoiding feeling so derivative.

Concocting different excuses for why the imperiled Burke and Irene must stick around on this doomed property, "The Nun" creatively runs out of juice before the third act and never rehydrates. The script is an example of missed opportunities and possible post-production tinkering. Plot threads are set up—such as the Vatican specifically and mysteriously instructing Father Burke to seek out the London-based Sister Irene to assist in the investigation—and then peter out without resolution. A crossword puzzle Demián Bichir's (2017's "Alien: Covenant") Father Burke is seen filling out initially poses a clue to the goings-on at the abbey, then is also forgotten. It is no secret Taissa Farmiga (2015's "The Final Girls"), sympathetic and convincing as Irene, bears a striking resemblance to older sister Vera, so to not link her character in any substantive way to Lorraine Warren seems borderline-foolish. "The Nun" is handsomely shot by Maxime Alexandre (2014's "Earth to Echo") and rich in atmosphere, but it cannot sustain itself on a darkly attractive veneer when there is little else about which to think or care. Once the film is over, one's understanding of the demon Valak is still murky and its link to characters previously established in "The Conjuring Universe" remain intangible. What is left is an inferior variation on increasingly wearisome scare tactics.