마취통증의학 전문의 차요한은 '닥터 10초'라는 별명답게 10초 안에 환자를 진단하고 치료 계획을 세울 만큼 실력있는 의사다. 환자를 아끼는 마음 또한 커서 그들의 고통을 덜기 위해 뭐든지 하고자 한다. 그래서 극심한 통증에 시달리는 말기 암 환자의 존엄사를 도왔고, 그 결과 감옥에 갇혔다. 요한은 감옥 안에서도 동료 재소자들의 건강을 돌본다. 출소 후 요한은 한세병원의 통증 센터를 이끌며 동료 의사들에게 영감을 준다. 어느 장소에서든, 어떤 직위를 달든 요한의 투철한 직업 정신과 환자를 사랑하는 마음은 변하지 않는다. 요한을 아는 사람들은 그를 존경하거나, 두려워하거나, 비난한다.
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. Yo Han is a promising doctor who needs only 10 seconds to figure out a patient's condition. While he is gaining fame with his outstanding skills, he confronts one patient who changes his whole life. Si Young is a doctor with a warm heart. Her family has been doctors for generations, and she takes after her mother's exceptional talent and her father's high empathic ability. But one day, Si Young 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.