After climate catastrophe and pandemic erase a third of Korea’s population, society fractures between the privileged citizens of a fortified Megacity and the refugees abandoned in flooded districts outside it. Gil Eun-mok escaped those ruins as a child and became a novice Catholic nun, only to return ten years later when five seemingly altruistic residents die under suspicious circumstances. Each death is staged like suicide, and each body is marked by a bouquet of white peonies. Eun-mok’s investigation crosses drowned neighborhoods, refugee camps, and the bureaucracy of the Megacity, forcing her to confront exploitation, class division, buried personal history, and the uneasy relationship between faith and justice.