To make ends meet, Yang-sun begins cross-dressing as a male bookseller, and meets the handsome and mysterious scholar Kim Sung-yeol (Lee Joon-gi), who works at the Hongmungwan. Sung-yeol is a vampire, and he continues to be haunted by the long-ago death of his first love Lee Myung-hee (Kim So-eun), especially when he meets Myung-hee's present-day doppelgänger Choi Hye-ryung, an aloof nobleman's daughter. Meanwhile, the evil vampire, Gwi (Lee Soo-hyuk), resides in the royal palace and uses his powers and political machinations to prevent the Crown Prince (Shim Chang-min) from ascending to the throne.