Park Ji-sang (Ahn Jae-hyun) is a doctor specializing in hepato-pancreato-biliary surgery in the best cancer research hospital in the country. He is also a vampire. Despite seeming cold and unfeeling, Ji-sang masks his soft heart and inner pain and yearns for closeness with people. He believes very strongly in the sanctity of human life, and suppresses his thirst for blood to treat terminally ill patients and save lives. Among his colleagues is Yoo Ri-ta (Ku Hye-sun), a hotshot physician who entered medical school at the age of 17 and is also the niece of the chaebol group chairman who owns the hospital. Ri-ta is highly capable but snooty and prideful, yet Ji-sang finds himself falling for her. He also gets drawn into a conflict between good and evil as he encounters Lee Jae-wook, a two-faced hospital director who gains everyone’s trust with his gentle demeanor, but inwardly harbors a dangerous ambition for power and a talent for cruelty.