A modern medical student accidentally transformed into Ren Ruyi, the younger sister of Zhu Yiwei Zuo of Anguo. In order to protect her from bloodshed, her sister hid her in a deep house and secretly taught her peerless martial arts, but she didn't know that the core of her body had been changed. Ren Xiaoxiao possesses martial arts talent that surpasses her sister's, and also conceals modern medical skills. While pretending to be an ignorant girl, she secretly detoxifies and heals her sister's injuries.
After Ren Ruyi joined the Wu Kingdom envoy team, she met the agency genius Yuan Lu. One is a fake sister who carries a secret, and the other is a short-lived young man suffering from heart disease. On the dangerous journey of escorting Princess Yang Ying, they went from temptation to falling in love, but they fell into trouble step by step because of the status of their family and country and the time limit of life and death. She can cure his illness, but she can't cure the poison of fate; he can break the trap for her, but she can't break up the destined separation. When Yuan Lu traveled thousands of miles to spread the military love, the silver needle in Ren Xiaoxiao's sleeve failed to catch up with his horse's hooves coughing up blood - the cold moon in Guanshan always reflected the unspoken "survive".
