Amidst the mermaid civil war, the Empress Princess Yun Ling —the heir with a sacred mission—stripped of her powers and exiled her to the mortal realm. Four merfolk closely tied to Yun Ling transformed into a doctor, a celebrity, a CEO, and a mafia boss to infiltrate the human world. Their quest: Find Yun Ling, uncover why she vanished... and confront her mortal incarnation, Xia Shi Yue, in a story of fire and tides.