The Nun (2018)

While "The Nun" may primarily be marketed as a horror film, it possesses a core mystery that drives its narrative, making it a worthy addition to a list of best mystery movies. The film centers around the unexplained and increasingly malevolent presence of a demonic force within a secluded Romanian abbey. Father Burke, an expert in demonic investigations, and Sister Irene, a young novice with a troubled past, are tasked by the Vatican to uncover the source of the evil and determine if the abbey is still holy ground. Their investigation into the mysterious deaths of the resident nuns, coupled with the oppressive atmosphere and cryptic symbols they encounter, propels a compelling whodunit where the "who" is a terrifying supernatural entity with a hidden agenda. The film's strength lies in its slow-burn unveiling of the truth behind Valak, the demonic nun. As Father Burke and Sister Irene delve deeper into the abbey's history and the dark secrets held within its walls, they unravel a complex puzzle piece by piece. Each clue discovered, each ritual deciphered, leads them closer to understanding Valak's motives and how to ultimately contain the evil. The mounting tension, coupled with the constant threat of the unknown, creates a gripping mystery that keeps the audience guessing until the final confrontation, solidifying "The Nun's" place as a worthwhile mystery film masked within the horror genre.