Jo Yang Sun is the daughter of a nobleman whose family loses everything when her father is framed for treason. To make ends meet, Yang Sun begins cross-dressing as a male bookseller, and meets the handsome and mysterious scholar Kim Sung Yeol, 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, especially when he meets Myung Hee's present-day look-alike Choi Hye Ryung, an aloof nobleman's daughter. Meanwhile, the evil vampire Gwi resides in the royal palace and uses his powers and political machinations to prevent the Crown Prince from ascending the throne. ~~ Based on a hit manhwa by Jo Joo Hee and Han Seung Hee.