Need Help to Structure a Murder Mystery Ritual Plot for D&D

Hello everybody. I am designing a mystery and horror mission for D&D set in a small, rural, and isolated town where the existence of the cult and the demon is completely unknown. The murders are being committed by a single man, a fanatic who follows an ancient ritual dedicated to Korgal, Lord of Blood and Rot. The players must discover the pattern of the ritual, interpret its cryptic verses, and protect the next victims, without ever being told explicitly who the next target will be. The ritual requires five human sacrifices, each based on a specific emotional or moral quality expressed in a poetic and ambiguous way: the Open Hand represents a kind person who gives without asking, the One Who Suffers in Silence represents an afflicted person with hidden pain, the Flesh That Burns represents a person ruled by desire, the Closed Fist represents a greedy and possessive person, and the Unbowed Brow represents a proud and arrogant person. The text of the ritual is cryptic and never names the sins directly, so the players must interpret each verse and relate it to the behavior of the town’s NPCs. When the five blood offerings are completed, Korgal can manifest or directly influence the world. I would really appreciate any advice since this is the first time I am running a session where investigation is important and I am not entirely sure how to handle it properly.

Sorry for my bad English, it's not my native language