Seungnyang is a young Goryeo-born girl who witnesses the traumatic death of her mother by the hands of General Dangkise, and grows up as a man to conceal her identity as a woman under the alias, “The Jackal”. Her reputation attracts the likes of Wang-Yoo, the deposed prince of Goryeo, who slowly begins to yearn for Seungyang’s love, not knowing that she is a woman. Seungnyang also starts to fall for him.
When Wang-Yoo is eventually crowned the King of Goryeo, Seungnyang meets Ta-hwan, the exiled prince of Yuan. After enduring a journey with Ta-hwan to escape his pursuers, Seungyang finds her long-lost father, who is tortured and locked in prison to die after Ta-hwan lied about her father under the pressure of Grand Councillor, without any knowledge that he was Seungyang’s father. Ta-hwan returns to Yuan as the new emperor, while Seungnyang’s identity as a woman is discovered by Dangkise and Wang-Yoo (after he is deposed once again), causing her to be taken to Yuan as either a water maid in the palace or Dangkise’s concubine. She vows to take revenge on Ta-hwan, who is now wed to Grand Councillor’s jealous and twisted daughter Tanashilli, is forcefully taken and ends up in the palace as a maid. However her identity is soon discovered by Emperor Ta-hwan, who begins to yearn and obsess over Seungyang, who is now known as Yang. Yang befriends other Goryeo-born people in the palace, such as Dok-man, Hong-dan, and Lady Pak, while also attracting danger due to the likes of Dangkise, who lusts after her. Meanwhile, Wang-Yoo is fighting a war with the Turks, led by Yon Bisoo, and wins, coming to Yuan to save Yang. He soon befriends the Grand Councillor in order to get close to his secrets and gain his trust, and is soon given the rights to take Yang out of the palace after an incident where she is tortured in prison. Yang soon becomes engaged to Wang Yoo and eventually bears his child, but in an attempt to leave the palace secretly with Lady Pak, Pak and other maids are slaughtered by Yeom Byung-soo and others under the command of Tanashilli out of jealously towards Pak’s pregnancy (Lady Pak was pregnant with Emperor Ta-hwan’s child). Yang gives birth to Star (Byul), but soon loses him after they are thrown off of a cliff; fortunately for Yang, she is saved by Jokho, an ally, but presumes her child to be dead. Meanwhile, Wang-Yoo and Ta-hwan are devastated by the death of Yang, with Ta-hwan losing his ability to talk and Wang-Yoo marrying in order to strengthen his ties with Grand Councillor and Yuan. Yang and Jokho are sold into the Eagle House, who plan on auctioning the two off to bidders. Yang is soon spotted by Tal Tal and Baekhan, who buy her. After consulting with Baekhan and Tal Tal, Nyang is chosen as the concubine representing their province, and soon surprises everyone in the Yuan palace, including Ta-hwan, who begins to show his favor for Yang. Empress Tanashilli grows jealous of Yang, and attempts to get rid of her any chance she has. She also has a son, Maha, who is actually the son of Yang and Wang-Yoo after he was found by a monk in the river. Unfortunately, her schemes come to an end after Grand Councillor is killed. Tanashilli is publicly hanged, and Dangkise, who is secretly living with Yeom Byeong-soo, watches and plans his revenge on Yang. Yang bears a son with Emperor Ta-Hwan named Ayushiridara, and Baekhan is named Regent. However, the Empress Dowager and Baekhan, who used to support Yang, begin to try and stop her from becoming Empress, for she is not of Yuan blood. Therefore, Baekhan brings his niece, Bayan Hudu, who seems kind and compassionate but is soon revealed to be sinister and cruel. Empress Dowager Budashiri raises Maha, Tanashilli’s son, and has him believe that Yang slaughtered his family, causing him to grow up hating Yang and Goryeo. Ayushiridara is the favored son of the emperor, and Maha is rejected by Ta-hwan due to the fact that he is believed to be Tanashilli’s son. However, Maha is soon slaughtered by Yeom Byeong-soo under the order of the Empress, and Yang discovers Maha was Star all along. Wang-Yoo soon realizes that Maha was his son, and is devastated by the loss of Maha. Meanwhile, Ta-hwan is growing insane from falsified letters of love between Yang and Wang-Yoo. Nyang and Tal Tal decide to kill Baekhan, who has grown corrupt and blinded by his own power. Bayan Hudu is exiled, and Tal Tal becomes the new Regent.
It is soon revealed to Ta-hwan that Maha was Yang and Wang-Yoo’s child by Dangkise, who is killed in his plan to exact revenge on Yang. Ta-hwan, after learning of the secret, decides to assassinate everyone who knew of the secret, including Wang-Yoo, in order to protect Yang. He kills Wang-Yoo, who professes he will always love Yang and protect her no matter what. Yang mourns the loss of Wang-Yoo, and becomes the Empress of Yuan. She orders the death of Bayan Hudu and those who are not loyal to the Emperor. It is soon revealed that the Emperor’s eunuch was the leader of Eagle House, and was feeding Ta-hwan a secret but lethal poison from which he will soon die.
In order to protect Yang and Ayushiridara, the Emperor kills his eunuch and exposes the Empress Dowager for her power-hungry ways. The Empress Dowager poisoned herself, Yeom Byeong-soo is stoned to death by Goryeo-born people, and Yang rules as the Empress Dowager with her son, Ayushiridara, who is the Crown Prince. During the invasion of Mongols, Tal Tal is killed in battle, and Ta-hwan dies in Yang’s arms, after she confesses she has always loved him. In a flashback sequence, Yang is riding with Ta-hwan before being scolded by Wang-Yoo for not being cautious with Ta-hwan. Ta-hwan defends Yang, and says that it was his order. Yang’s horse is gone, and she must choose between Wang-Yoo and Ta-hwan