Unable to withstand an attack by the Great Qin dynasty, the small border kingdom of Mobei chooses to cede territory and sue for peace, even sending its crown prince, Mo Changfeng, to Great Qin as a hostage. Under the care of Princess Qin Biyao, Mo Changfeng finds a brief respite from his humiliating life. He also briefly bonds with Qin Jiangmo, the crown prince of Great Qin, and Yuwen Jun, the chancellor’s son, as they drink and hunt together.
A royal autumn hunt is upended by the arrival of Yu Wan'er, a commoner girl, disrupting the balance among the three noble young men. At the same time, the king of Mobei invades Great Qin to seek revenge, only for his forces to be crushed. The king is captured and beheaded in public. Thanks to Princess Qin Biyao’s intervention, Mo Changfeng escapes execution, but he is placed under house arrest for three years. With Yu Wan'er’s wholehearted help, he manages to flee back to Mobei after three years. From then on, his thirst for revenge twists him into a monster. He later plots to kill Yuwen Jun, the commander leading Great Qin’s army. To save Yuwen Jun, Yu Wan'er chooses to die with Mo Changfeng.
