Su Wan, a doctor of modern forensic toxicology, traveled through time and became the scapegoat of a "mute woman" who was about to be sent to the guillotine. At the critical moment of life and death, she relied on a silver needle to reverse the situation, and was taken back to the government office by the cold-faced prince Lu Beichen. From then on, she used the silver needle as a knife to open up the injustices in the world; he used power as a shield to protect her. The two teamed up to investigate the bizarre murder case in the border town and the treacherous imperial case in the capital.
