Lin Qingyao, the legitimate daughter of the Chancellor's family, accidentally discovers her fiancé, the Crown Prince, involved with her younger half-sister before their wedding. Instead of receiving justice, she is pressured by her family to marry the memorial tablet of the Third Prince, who supposedly died in battle, in her half-sister's place. To protect her seriously ill younger brother, she chooses to endure the humiliation and compromise, eventually earning the Emperor's favor through her exceptional courage and intelligence. Meanwhile, Xiao Jingchen, the Third Prince who never actually died and has assumed the identity of a guard to investigate the case in secret, offers her his help, and the two form an alliance. Together, they gather evidence and gradually expose the numerous conspiracies involving her stepmother, biological father, and the Crown Prince, who have colluded for personal gain. As they face one crisis after another side by side, they gradually fall in love. In the end, they expose all the forces behind the schemes, clear the unjust accusations, and finally bring justice to those who have suffered.