Wol Yeon of the great Yeon clan in the Kingdom of Asatae is a spirited girl who dreams of becoming a general one day. Her dreams are crushed when the royal government mercilessly eradicates her clan, murdering everyone, including Wol's parents. Wol is left with no one she can trust but her tutor Jae-i, who proceeds to raise and train her as a master assassin so that she may take revenge against the king. Eight years later, Wol successfully infiltrates the palace to kill the king, only to find that all is not as it seems...