Abandoned by his mother shortly after immigrating to America, Gon is raised by the mafia and grows up to become a cold-blooded hitman. Though usually flawless in taking out his targets, Gon makes a terrible mistake of killing an innocent young girl. Swamped by feelings of regret, guilt and shame, Gon no longer wants to be a hitman, but his boss gives him one last mission. So Gon finds himself in Korea, the land of the mother that abandoned him, on the trail of his last target. But in bitter irony, that target is Mo-gyeong, the mother of the dead child. Mo-gyeong is a risk manager at an investment firm who now lives in a fog of despair, caring for her senile mother while reliant on alcohol and drugs to get by following the loss of her husband and daughter. She is oblivious to her involvement in a much larger conspiracy until a man approaches her, claiming to know the truth behind her daughter's death. Gon agonizes and faces a life or death choice ― to follow the order to kill his target or to risk his own life at the price of redemption for his past.