Gu Zheng, the Great Marshal Who Guards the Desert Frontier, returns home in triumph after eight years defending the borders. Along the way, he encounters the powerful local tyrant Zhao Chen abducting an innocent woman, Ye Wanqing, and steps in to rescue her. In retaliation, the Zhao family conspires with Li Song, the magistrate of Xining County, leading to the destruction of the Gu family home and Gu Zheng's arrest. Ye Wanqing presents Gu Zheng's imperial tiger-head token to the provincial governor, exposing the truth. Li Song flees to the residence of his brother-in-law, Song Mingyuan, the prefect of Yonggu. To protect himself, Song Mingyuan poisons and gravely injures Gu Zheng's father, then orders every medical clinic in the city shut down. Gu Zheng encounters Su Mo, a reclusive female physician, and discovers a clue to saving his father. Following the trail, he uncovers the true mastermind: the Marquis of Anping. Gu Zheng gathers evidence that the marquis embezzled disaster relief funds, secretly manufactured weapons, and operated an illegal prison. He escorts the marquis to the imperial capital and exposes the corrupt officials before the emperor in the Golden Hall. After restoring peace to the region, war breaks out once again on the northern frontier, and Gu Zheng bids farewell to his family and the people.