Set in the 18th-century Joseon, it tells the story of Crown Prince Lee Sun (Yoo Seung Ho) and his fight against a powerful and wealthy organization Pyunsoo-hwe that controls the country behind the scenes due to its monopoly of the nation’s water supply. With the help of the woman he loves named Han Ga Eun (Kim So Hyun), Lee overcomes adversity and grow as a just ruler.