Forced to marry the crippled Crown Prince in her elder sister's place, Ajiu is given a silencing drug and endures endless contempt, yet survives in the Eastern Palace through her own strength. Bearing humiliation and hardship, she secretly delivers confidential letters for Zhao Heng and retrieves account books and defense maps, helping him regain his power. With her by his side, Zhao Heng rebuilds his confidence, secretly trains his legs, and gathers strength. On the night the Second Prince stages a coup, Zhao Heng strikes back and ascends the throne. No longer a substitute, Ajiu is personally crowned Empress Jing Shu by the emperor. From substitute bride to empress, she steps out of the shadows and becomes the one light illuminating his life.