About a man and a woman who miss each other but cannot meet. Young-ho, a young man who took several tries to get into college, doesn't have any special goals in life, and starts exchanging letters with someone.
Ex intelligence agent Ki-heon is tasked with safely transporting Seo Bok, the first ever human clone, who holds the secret of eternal life. Several forces try to take control of Seo Bok to serve their own agendas.
Behind a beautiful face hides a cruel nature—Baek Ah-jin, who sees through and manipulates others' hearts. After stepping on the sacrifices of many to reach the top, everything begins to change the moment she arrives there. A woman wearing a mask to escape hell and climb to the highest place. And the story of the Xs being brutally crushed by her.
