Meet Seon-ji (Lim Yoon-a), a lovely aspiring pâtissier with a secret that even she herself is unaware of: She is under a curse that transforms her into an unmanageable she-devil every night. Daytime Seon-ji has no recollection of Nighttime Seon-ji and the latter’s ungracious behavior. One summer night, Nighttime Seon-ji bumps into her awkward and jobless neighbor Gil-gu (Ahn Bo-hyun) in a spectacular fashion. Seizing this opportunity, Seon-ji’s family hires Gil-gu to work the nightshift of watching over her. While crushing hard on Daytime Seon-ji and navigating their bewildering late-night dates, Gil-gu becomes determined to unravel the curse and help both versions of the girl find their own futures.