The 1920s were a time of enormous change and turmoil in America, with terrifying creatures sprouting across the country. The religious organization known as the Order of Magdalene was founded to confront this threat. The New York chapter of the organization is home to the youthful and wild Sister Rosette Christopher, as well as her boyfriend Chrno. Despite incurring severe collateral damage on their operations, the famed crew is exceptional at exterminating demonic threats. Rosette and Chrno, on the other hand, are both motivated by their dark pasts. Rosette thinks that through exterminating demons, she would be able to recover her missing brother Joshua, who was kidnapped by the sinner and demon Aion, with whom Chrno also has a violent past. The two of them must combat the growing threat of demonic possession.