A forgetful killer can be a dangerous thing. Noh Ji Wook (Ji Chang Wook) is a prosecutor who changes jobs to become a private attorney at a powerful law firm. Meanwhile, Eun Bong Hee (Nam Ji Hyun) is a prosecutor trainee who works with prosecutor Cha Yoo Jung (Nara), Ji Wook’s ex-girlfriend who desperately wants to win him back.
In the 1700's, Crown Prince Lee Sun (Yoo Seung-Ho) fights against Pyunsoo hwe. Pyunsoo hwe is an organization that has accumulated power and wealth through privatizing water all over Joseon. Crown Prince Lee Sun becomes a hope for the people who suffers. Ga-Eun is the woman Crown Prince Lee Sun loves and she helps grow as a ruler.