Mermaid girl Bao Rourou is searching for her missing father when a murder case drags her into the path of royal detective Gu Xinghe. Forced to work as his assistant, she gradually becomes part of his investigation, while he keeps probing her true identity in secret, hoping it will lead to a cure. Side by side, they untangle a string of bizarre crimes and slowly fall for each other. The clues they uncover point to a larger plot behind every case and to the mystery of her father’s disappearance. With their friends at their side, they save him—yet before their promise of a lifetime can even settle, another crisis comes crashing in…
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