Ja-yoon is a high school student who struggles with memory loss after she endured some unknown trauma during her childhood. While trying to uncover the truth, she is unwittingly dragged into a world of crime and finds herself on a journey that will awaken many secrets hidden deep within.

Kingdom of Goguryeo, ancient Korea, 645. The ruthless Emperor Taizong of Tang invades the country and leads his armies towards the capital, achieving one victory after another, but on his way is the stronghold of Ansi, protected by General Yang Man-chu, who will do everything possible to stop the invasion, even if his troops are outnumbered by thousands of enemies.

Tae-sik is a so-called "Hit Man" of a gang. But after his boss dies, the gang falls apart; and during a power struggle, Tae-sik's close gang member Gi-sun is murdered. Gi-sun was like a big brother to Tae-sik so he vows revenge. With the help of the dirty cop, Detectvie Han, Tae-sik is introduced to a woman named Mae-hwa. She provides clues for the murder and the two bond over their search for the killer. But during their search, Mae-hwa asks too many questions and it rubs the wrong people the wrong way that makes her end up being in danger; and now it is up to Tae-sik to rescue her.