A dogged detective in pursuit of a faceless drug kingpin gets a much-needed break when a survivor from a mysterious factory explosion decides to help.

Set in 1398. Kim Min-Jae (Shin Ha-Kyun) is the supreme commander of the Joseon Dynasty. He falls in love for the first time and for that woman he takes risks. Yi Bang-Won (Jang Hyuk) is the King’s son. He helped his father setup the Joseon Dynasty era, but he was not picked as the Crown Prince. He still holds ambitions of becoming the King one day. Jin (Kang Ha-Neul) is Kim Min-Jae’s son and the King’s son-in-law. Due to his position as the King's son-in-law, he is unable to take part in politics and only seeks out pleasure.

Whenever elementary school teacher Kang Joon-soo (Lee Seung-gi) falls in love, he always gives too much of himself to the relationship. Yet despite that, he ends up being the one getting dumped by his girlfriends. Joon-soo has been friends for 18 years with Kim Hyun-woo (Moon Chae-won), a weather forecaster whose beauty belies her witty tongue and aggressive manner.