Season 1

Go Won Pyo of the Gyeru Tribe comes before King Pyeongwon and threatens him with his private army for the exclusive rights to salt. Despite the King's unrest, Queen Yeon leaves for patrol taking Princess Pyeonggang with her. Meanwhile, On Hyeop the chief of the Sunno Tribe tests his son's manhood. Part 2: While Queen Yeon visits On Hyeop, Go Won Pyo arrives on King Pyeongwon's decree to kill Queen Yeon and Princess Pyeonggang. Princess Pyeonggang escapes with Dal's help as Oh Hyeop and Queen Yeon confronts Go Won Pyo. Meanwhile, King Pyeongwon looks for Wol Gwang, Queen Yeon's secret lover.

Eight years go by and although Yeom Ga Jin wants to live a humble, quiet life, she has one last mission to complete, to assassinate King Pyeongwon. On her way to the palace, she saves On Dal's life but does not recognize him, and they go their separate ways. Meanwhile, Go Won Pyo prepares an attack on the King during the farewell ceremony for the late Queen Yeon. On Dal saves Ga Jin and nurses her back to health. While she recuperates, her companions hear about her failed attempt and search for her. When they find her, they remind her of their rule to kill anyone who sees their face or to marry him to make him one of their own. Meanwhile, Go Won Pyo tells his son, Go Geon, to protect the palace.

Ga Jin rushes back to Cheonjubang after hearing that her father was in trouble due to her failing her mission to assassinate King Pyeongwon. On her return, Du Jung Seo releases her father, Yeom Deuk, but instead holds her captive after she asks about her past. Meanwhile, On Dal hears of Ga Jin's predicament and rushes to save her.

King Pyeongwon believes he is seeing the ghost of Princess Pyeonggang as she stands in front of him in the flesh. However, Ga Jin escapes with help from Go Geon who she remembers but not without being warned of her fate if she returned as an assassin. Meanwhile, hanging upside down, On Dal waits for her return.

Go Geon reports to King Pyeongwon that Princess Pyeonggang is alive, showing him the jade necklace as proof. He promises to bring her back safely to the palace without his father, Go Won Pyo, knowing about it. Meanwhile, Ga Jin tries to change On Dal's heavy conscience as he turns his back on her.

On Dal and Ga Jin strike water and bring joy to Ghost Valley. However, despite the happiness, Ga Jin comes face to face with Du Jung Seo who tells her about the twins. She is left to decide whether to save them and break her promise of not killing again. Meanwhile, Go Won Pyo gives three hundred mounted men and three hundred soldiers to Go Geon after seeing King Pyeongwon.

On Dal gets released from holding and reunites with Pung Gae, Weol, and the Tara twins while Ga Jin returns to being the Princess. Although they all are astonished at her royal descent, On Dal believes she will return to them. Meanwhile, Go Won Pyo meets Hae Mo Young and plots to hurt the Princess.

Thanks to Geon and Dal’s help, Ga Jin manages to save the women from being sold off to Silla. After returning to the palace, Ga Jin suggests that the King should punish Hae Ji Weol for trying to sell the women as contributes to Silla. Meanwhile, Gochuga tells Geon that he doesn’t have to leave for the borderline.

The candidates for the royal wedding are called into the palace. However, it is Gochuga’s plan to make Ga Jin and Geon get married. Dal hides his identity and sneaks into the palace, but he gets caught by Geon. The King calls in Ga Jin and demands an explanation about their relationship. Ga Jin lies to the king that they are already married, and the king tells her to leave the palace.

Ga Jin and Dal come to Ghost Valley to live with Lady Sa. They lie to her that they are now married, hiding the fact that they are there to train Dal in swordsmanship. However, Lady Sa has a hard time accepting the princess as her daughter-in-law. Meanwhile, Geon becomes the Crown Prince’s trainer, but the young prince refuses to leave his chambers.

Despite Lady Sa’s anger at Dal’s decision to train in swordsmanship, he is determined to become a general like his father. Soon, his skills surpass the level at which Ga Jin can train him. She suggests that Dal go to study with a new master, and the pair set off to find him. Meanwhile, Mo Yong and the chief of Cheonjubang convince Royal Consort Hyeon to do a ritual.

After saving Ga Jin and Lady Sa by killing the men sent by Go Won Pyo, Dal falls into a state of shock. In order to help him find his path again, Ga Jin speaks to Un Am and Lady Sa about General On’s wishes for Dal. Meanwhile, Geon corners Mo Yong with his knowledge of her identity. Then Mo Yong is asked to carry out a dangerous task by Gochuga.

The Northern Zhou army marches ferociously down south. Bearing his weak body, King Pyeongwon calls upon all tribes to battle. The Sunno Tribe also stands up for war, whereas Gochuga sees this as an opportunity to fulfill his desire. Goguryeo faces a vast danger that will decide the fate of the nation. The only solution is for the five tribes to unite and fight as one.

Du Jung Seo poisons King Pyeongwon and Crown Prince Won, but Ga Jin and Dal save them just in time. As the King orders the incident never be spoken of, Ga Jin suspects the Queen’s intentions. Meanwhile, the people of Sunno Tribe prepare to move the Pyeongyang Castle, but Lady Sa refuses to go with Dal.

The Princess succeeds in luring Go Won Pyo and the Queen into her trap. In return for not exposing the two, she demands one thing from each of them. Slowly gaining power within the palace, the Princess falls deeply into the concern of how to deal with the Go Family. However, the Go Family’s response still seems unpredictable.

Dal volunteers to lead the troops to Hwangju Fortress and subdue the revolt that has broken out. However, when Ga Jin shows up after the fighting has subsided, she and Dal argue about how to proceed from there. Meanwhile, the news of more revolts at other fortresses arrives, and Gochuga bides his time to attack the palace.

Go Won Pyo and his son are thrown in prison. As they await their punishment, a small moment of peace finds its way to the palace. Meanwhile, Lady Sa takes a journey to the capital to visit Dal for the first time in a while. However, not long after her visit, Tara Jin comes by with news of an attack against the palace. Pyeonggang and Dal prepare for battle and whatever fate may come.

It is now four years after Gochuga’s death, and Crown Prince Won sits on the throne of Goguryeo. Pyeonggang fights war after war to help the young king, but her brother seems to misunderstand her intentions. Meanwhile, Dal lives like a hermit in the woods, and Geon lives as a drunkard in Silla. However, he suddenly decides to return to Goguryeo.

Go Geon comes back to Goguryeo as an envoy of Silla. As the palace of Pyeongyang is in a state of unrest with his presence, King Yeongyang thinks deeply of what to do with him. Meanwhile, On Dal lives lonely in the mountains until he hears some unexpected news. Not knowing the true intentions that Go Geon holds, the tension within Pyeongyang palace thickens.

King Yeongyang decides to send reinforcements to Adan Fortress where Pyeonggang and Dal fight to defend it. Dal commands Pyeonggang and Jin to take the wounded back to Pyeongyang Castle, but Pyeonggang has plans of her own. As he awaits the Silla army to attack, Dal receives a letter from King Jinheung instead.