The general protecting the country, Ling Zhan, was falsely accused of treason and his entire family was executed. The only daughter, Ling Shuang, escaped by chance and concealed her identity to become a street violinist; Ling Shuang hid a guqin passed down by her family, with a soft knife hidden in the belly of the piano. She used the sound of the piano to hide the shadow of the knife and survived in the border town; the swordsman Yeying was ordered by the powerful officials to hunt down Ling Shuang, but was shaken while listening to the piano and rescued Ling Shuang. The two were forced to flee together. Ye Ying's identity was mysterious and seemed to be related to the old affairs of the Ling family; Ling Shuang discovered his father's legacy from the secret code in the piano, which pointed to the dispute between the powerful officials in the capital and the prince; the two decided to go to the capital, but encountered several interceptions on the way. Yi sneaks into the mansion of a powerful minister, while Ye Ying sneaks into the world; Ling Shuang learns that his father was involved in the conspiracy to depose the prince, and the powerful minister wants to use the prince's hand to usurp the throne; Ye Ying's true identity is Ling Shuang's long-lost brother, who was sent away by his father to study art; the brother and sister recognize each other, but they have differences over the method of revenge; Ling Shuang advocates using evidence To clear their grievances, Ye Ying insists on retaliating with teeth; the powerful officials notice the two of them and set up a deadlock. Ling Shuang sets up an array with the sound of the piano, and Ye Ying defeats the enemy with the shadow of the sword; finally they join forces to break into the palace, expose the conspiracy of the powerful officials, and the prince is restored to power; Ling Shuang gives up the title, and retreats to the mountains with Ye Ying; there are still shadows surging in the distance, but the heart of the piano is strong, and the shadow of the knife is with him.
