People think it is a doctor’s bounden duty to save a patient’s life. But things are different now. Things are needed to be considered other than saving one’s life. Modern medicine has been developed remarkably, and it is quite possible to save a person's life who is on the verge of death. But we need to think about if prolonging a patient’s life makes the patient truly happy. Cha Yo Han is a promising doctor who needs only 10 seconds to figure out a patient’s condition. While he is gaining his fame with his outstanding skills, he confronts one patient who changes his whole life. Kang Si Young is a doctor with a warm heart. Her family has been doctors for generations. She takes after her mother’s exceptional talent and her father’s high empathic ability. But one day, she suddenly leaves the hospital. After a year later, she goes to the penitentiary to serve as a temporary medical doctor, and she meets a prisoner who was a former doctor. He is a genius who can grasp the patient’s condition within 10 seconds. After meeting him, Si Young’s life totally changes. And the day she comes back to the hospital, she meets the prisoner again, and this time, he is a professor. Doctor John is a human medical drama of anesthetists who seek the cause of mysterious pain their patients suffer, like detectives chasing after a suspect.