In the fictional rural city of Seopju, an old curse awakens when stolen funeral money releases the Cow Woman spirit and her husband, the Snake King. After the spirit possesses schoolteacher Kang Seo-kyeong, snakes begin appearing throughout the town and people who once tormented her start disappearing or dying. Police investigator Jo Yeong-ho joins forces with a shaman-in-training to determine whether the deaths are supernatural vengeance or the work of a human killer. Moving through cemeteries, shrines, possessed bodies, and ritual spaces, Seopju combines crime investigation with Korean shamanic belief, turning social resentment, guilt, and spiritual revenge into a distinctive contemporary occult thriller.