Chen Laoqi, an old boatman at the Qinghe Ferry, has spent forty years ferrying people across the river. After a torrential downpour, he discovers a black flood dragon named Ao Chuan trapped beneath a bridge by dragon-subduing chains for twenty years. Saving him draws Chen Laoqi into an old case involving the Qinghe River Palace and uncovers the truth behind the flood five years ago and the deaths of A-He's parents. As the crimson fiend beneath the river awakens and the seven meridians spiral out of control, Chen Laoqi must rely on a battered boat and a water-cutting blade to see this perilous crossing through, caught between raging floods and supernatural monsters.