Nok-Du, who is living on a small island, witnesses his father and brother get attacked by a group of assassins. He decides to leave home and find out who they are and work for. He follows the leads and arrives in Hanyang.

Nok-Du disguises as a woman and enters the village where only widows are allowed to live. Fortunately, no one is suspicious of Nok-Du yet. He finds out that there's a gisaeng house right next to the widow village.

At night, Nok-Du happens to overhear the conversation of a group of widows who look like trained assassins. Nok-Du starts to follow one of them into the woods. Meanwhile, Nok-Du's father and brother move from the island to the mainland. Yun-Jeo, Nok-Du's father, decides to go to Hanyang to take care of unfinished business.

Nok-Du and Dong-Ju become close. Nok-Du helps out Dong-Ju when she is having a hard time because of her injured hands. Dong-Ju says that she wants to treat Nok-Du like an older sister. Nok-Du happens to see a shaman and widows performing a religious ceremony, and he thinks that the widows are scheming something.

Dong-Ju realizes that Nok-Du has been pretending to be Lady Kim so far. Nok-Du persuades Dong-Ju to let him stay in the village. The widows talk about a man who sneaked into the village last night, and they plan to catch him by making a composite sketch of him. Nok-Du decides to give the widows misleading information about the man to confuse them.

Dong-Ju hears a rumor about the man who broke into the village the other day. She realizes that it is not a good idea to let Nok-Du stay in the village. She asks Nok-Du to leave the village. Meanwhile, Nok-Du finds out that a group of widows is planning to kill someone, and he makes a deal with the widows.

Nok-Du decides to help Dong-Ju so she doesn't have to be a gisaeng. Nok-Du gives up the mission that the widows of Muweol Corps gave him. He goes to meet Lady Cheon with an idea that can help Dong-Joo. Meanwhile, the widows of Muweol Corps agree to give Nok-Du the second chance and order him to complete another mission.

Dong-Ju keeps being reminded of her childhood and family after she came to Hanyang. She visits the house she used to live when she was a child. That's when she runs into Yul-Mu. And Nok-Du happens to watch them have a chat from afar. Nok-Du manages to complete his mission, but he hears that the real Lady Kim and her servant got caught.

Nok-Du returns to the village for widows with Dong-Ju and Yul-Mu after completing his mission in Hanyang. However, the widows and gisaengs in the village think that Nok-Du likes Yul-Mu. Meanwhile, Yun-Jeo and Hwang-Tae see that a group of assassins are in front of their place. They start to run away from the assassins.

Nok-Du is curious about who Dong-Ju likes. He asks her who it is, but she never tells him. Nok-Du decides to tell Dong-Ju his feelings for her, but Dong-Ju tries to keep her distance from Nok-Du.

Yul-Mu finds out that Nok-Du has been pretending to be a woman all this time and that Dong-Ju has been looking out for Nok-Du. Yul-Mu wants to know if Dong-Ju has feelings for Nok-Du. And Nok-Du tells Dong-Ju that he will make her fall in love with him.

After the widows of Muweol Corps left for Hanyang to kill the local functionary, Nok-Du and Lady Cheon find out that the widows are in a trap. Lady Cheon asks Nok-Du to go help out the widows, and that's how Nok-Du becomes a member of Muweol Corps.

Heo Yun and his fellows think that the King might have noticed about their plan, so Heo Yun orders the widows of Muweol Corps to move their base. And Heo Yun encounters Hwang-Tae. Meanwhile, Nok-Du happens to overhear the conversation between Dong-Ju and Yul-Mu, and finds out that Dong-Ju is planning to leave.

Nok-Du meets Hwang-Tae at Yul-Mu's house. Nok-Du insists that he and Hwang-Tae should hurry and leave the place, but Hwang-Tae refuses. Instead, Hwang-Tae tells Nok-Du a big secret.

Because of the attack by Yul-Mu's underlings, the village for widows is destroyed and many widows get injured or killed. Nok-Du risks his life and helps the widows without disguising himself.

In Hanyang, Dong-Ju is trying to get a job in the palace by bribing court ladies. One day, a court lady asks Dong-Ju to find a man for her. Dong-Ju manages to find a man who matches the description. Meanwhile, Nok-Du visits Heo Yun again. Heo Yun takes Nok-Du to the room where Yun-Jeo is staying.

When the widows of the Muweol Corps are confused and want to find out who is behind the death of Lady Cheon, Yul-Mu tells them that it was Heo Yun's order. He also suggests that the widows help him to create a new world. Meanwhile, Nok-Do tells Dong-Ju that he will never let her leave him again until she pays back what she owes him.

When Nok-Du and Dong-Ju are walking on the streets, an old lady stares at Dong-Ju as if she knows Dong-Ju. And Nok-Du and Dong-Ju run into the King again. The three of them go hiking to relieve the King's insomnia.

Nok-Du finally meets the King at the palace and is assigned to assist a senior chief administrative officer. Meanwhile, Heo Yun visits the King to warn that Yul-Mu should not be trusted and is plotting treason.

Heo Yun continues trying to convince that Yul-Mu is plotting treason, the King still doesn't believe him. Nok-Du runs into the Queen in the palace and notices that she is wearing the same jewel as the one he possesses.

The King pays his visit to Heo Yun who is imprisoned in the dungeon, but this time, the King comes with Yul-Mu, Hwang-Tae, and two widows. Hwang-Tae and the widows make the false testimony to make Heo Yun a traitor. Meanwhile, Dong-Ju finally gets a job at the palace. Nok-Du visits her workplace and helps her work.

Yul-Mu finally finds Dong-Ju in the palace. He tries to take her somewhere, but Nok-Du stops him. Meanwhile, Yun-Jeo and the Queen secretly meet in a private house. Yun-Jeo tells that the Queen's son is still alive and that she should protect him from the King. Then, the door is opened, and an uninvited guest comes into the house.

Jung Yun-Jeo is taken to the prison, and Dong-Ju is shocked that the Chief Administrative Officer is the King. The King begins to torture Yun-Jeo. Every time he aims the sword at Yun-Jeo, he keeps seeing the face of Heo Yun, which makes him pass out.

Nok-Du plans with Ssook to steal the Merit List from Grand Prince Neungyang (Yul-Mu). In hopes of ruining the plan, Nok-Du goes to see the King with the Merit List. When Nok-Du sees the King and Yun-Jeo in prison, he happens to hear what’s truly on the King’s mind.

Dong-Ju finds out that Nok-Du is the biological son of the King she’s been despising for her life. Knowing the consequences that could be brought upon them, she ponders their relationship. Meanwhile, Nok-Du is promoted as the Royal Guard and is ordered to stay by the King at all times.

Nok-Du spreads the rumors around the town about the King and himself. He plans to murder the King and undo the injustices that were caused due to him being alive. Dong-Ju also plans to not hide. Therefore she decides to end her relationship with Nok-Du.

Dong-Ju escapes from the palace and moves alone to kill the King. Meanwhile, Nok-Du escorts the King to his way to the shrines. One night, the King offers a drink to Nok-Du. He honestly shares his true feelings of loss in never being loved by his own father.

The revolting army takes over the castle. Everyone seems to be after the King, but the King himself just realizes that his trusted royal guard Yeon-Su is actually Nok-Du. Enraged with betrayal, the King goes out in the middle of the night to search for Nok-Du.

Dong-Ju can’t sit still and wait for Nok-Du. She gathers her things and sets off to the palace to see how things are going. She enters the palace to see Neungyang (Yul-Mu) aiming at Nok-Du and throws herself in front of his arrow. The battle continues and surprising news is shared throughout the palace.

Nok-Du and Dong-Ju manage to get out of the palace thanks to the Queen's help. Yul-Mu and his men go after Nok-Du and Dong-Ju. However, Nok-Du and Dong-Ju end up being surrounded by Yul-Mu's armed forces.

Nok-Du volunteers to keep working with the widows. And the wedding ceremony for Nok-Du and Dong-Ju is held. Every resident on the island comes to celebrate the couple.