Living a double life, Chilwu (Moon Jung-Hyuk) is nothing but a negligent officer in the daytime, but at night he turns into a charismatic leader of five assassins standing up against injustice and brutality committed by the wicked in the 17th century Joseon Dynasty. Enraged at his innocent sister's death, our hero makes a 180-degree transformation, changing into an assassin to fight against the corrupt world. Watching swashbuckling action scenes including Eric’s rousing swordplay and flamboyant martial arts, viewers find themselves gradually unmask a conspiracy and mystery surrounding Chilwu’s assassin group.