Cha Yo-han (Ji Sung) is a doctor of anesthesiology. He is arrogant, but he is a genius at his work. Kang Shi-young (Lee Se-young) is a resident of anesthesiology who works with Cha Yo-Han. She is smart, warm and listens carefully to her patients. People, with mysterious acute or chronic pain come to the hospital. There, Cha Yo-han and Kang Shi-young try to find the causes of their pain. Son Seok-ki (Lee Kyu-hyung), a prosecutor who is against the practice of euthanasia. He was the prosecutor during Yo-han’s trial and wanted to sentence him to ten years in prison. He holds a grudge against the Yo-han, the doctor who ended the life of his son’s murderer.