Lin Qingyao, the legitimate daughter of the Lin family, disguised herself as a man for twelve years while defending the northern frontier, earning her military honors and the title of Great General Who Protects the Nation. Crown Prince Xiao Jingyan fears the Lin family's power, so he fabricates false evidence and attempts to implicate the entire Lin family during the morning court assembly. Lin Qingyao sheds her feminine disguise and appears before the court, publicly exposing the crown prince's forged letters and conspiracy with the barbarians. Former frontier generals step forward to testify, and the truth comes to light, leading to the crown prince's deposition. Impressed by her loyalty and bravery, the emperor issues an edict allowing women to serve in the military and hold official positions. Prince Xiao Jingheng, the Ninth Prince, grateful that she once saved his life, volunteers to go to the northern frontier and stand beside her in defending the border.