A modern medical student unexpectedly transmigrates into the body of Ren Xiaoxiao, younger sister of Ren Ruyi, Left Envoy of the Red-Clad Guards of An Kingdom. To keep her away from bloodshed, her sister hides her away in a secluded residence and secretly teaches her peerless martial arts, never realizing that someone else now inhabits the body. Ren Xiaoxiao possesses greater martial arts talent than her sister, along with modern medical knowledge. She pretends to be an innocent young girl while secretly helping her sister detoxify and recover from her injuries.
After joining Ren Ruyi’s diplomatic mission to Wu Kingdom, she meets Yuan Lu, a genius mechanic. One is a fake younger sister burdened with secrets; the other is a short-lived young man plagued by a heart condition. As they escort Princess Yang Ying through one perilous journey after another, they go from testing each other to falling in love, only to be torn apart step by step by their duties to their countries and the limits of life. She can treat his illness, but not the poison of fate; he can dismantle mechanisms for her, but can’t undo the separation awaiting them. When Yuan Lu races a thousand miles to deliver military intelligence, the silver needles hidden in Ren Xiaoxiao’s sleeve still can’t catch up with his bloodied horse. Beneath the cold moon over the mountain pass, what shines through is always the unspoken plea: “Stay alive.”
