[1] Kang Yu-jin, a wealthy biology professor doing a butterfly field study, takes in a new housemaid; the young woman, Mi-ok, is the daughter of a shaman priestess who recently died in a house fire.

Having suffered from nightmares about exactly the same doll, Seon-hee becomes increasingly suspicious and paranoid that Mi-ok is trying to kill her and usurp her household.

From then on, Seon-hee is tormented horribly by visions of the doll attacking her and it starts to take a great toll on her sanity.

[3][4] In a review for Koreanfilm.org, Darcy Paquet cited Suddenly at Midnight as a rare example of 1970s-80s Korean horror that was genuinely frightening, describing it as "a mysterious psychological study... that beguiles the viewer right up to its bizarre closing image."

He praised the film's direction, saying, "Ko has a good feel for how to create tension from precise editing and the patient accumulation of evocative details", and also credited actress Kim Young-ae for a "convincing performance as the panicked wife".