Lin Hai, a young man, is betrayed by his own uncle, who tries to kill him by kicking him into the sea. At this critical moment, he is rescued by Ning Xi, a young mermaid. To repay his kindness, Ning Xi commands the sea creatures to help Lin Hai escape death with a bountiful haul of precious seafood. Armed with a mermaid's scale, he wins back the fishing boat his father left behind, only to accidentally uncover an underwater secret belonging to Hanyang Group. With a dangerous battle unfolding at sea on one side and the mermaid's assistance on the other, Lin Hai investigates step by step, vowing to uncover the truth behind his father's disappearance.