The Yellow River, Yangtze River, and Lancang River originate from the same source, and three families known as "Water Evils" (Ding, Jiang, and Yi) live along the river. What are "Water Evils"? They can move freely in the water and possess the skills of geomancy, feng shui, and treasure hunting. Yi Sa, the last Water Evil of the Yi family, runs an "underwater bank" business along the Lancang River. During a "Golden Fortress" excavation, Yi Sa encounters and saves Zong Hang. To uncover the truth of what happened and to save himself, Yi Sa trains Zong Hang to become a professional Water Evil, and together with Ding Yudie, a Water Evil from the Ding family, the three enter the "Ancestral Golden Fortress."