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.