The film is a domestic horror, following the story of an upper-middle-class family falling into destruction due to the introduction of a sexually predatory femme fatale housemaid into the household.

A piano teacher, Mr. Dong-sik Kim, reads a newspaper story to his wife about a man falling in love with his maid.

Miss Cho attempts to further pursue Mr. Kim by taking up his offer of piano lessons, which he proposed to help earn more income during his wife's pregnancy.

At the factory, Miss Cho learns that her friend has committed suicide after being fired, due to being overcome by the pressure of not being able to secure a new job.

Mr. Kim eventually decides to come clean to his wife, who, despite her initial depression over the affair, convinces Myung-Sook to throw herself down the flight of stairs that leads to the second story, which successfully results in her having a miscarriage.

She forces him to move upstairs into her room while Mrs. Kim labors over her sewing machine, falling asleep at her work every day.

The film's narrative has apparently been told by the piano teacher, who then warns the audience that this is the sort of thing that could happen to anyone.

Comparing the director to Luis Buñuel, Frodon wrote Kim is "capable of probing deep into the human mind, its desires and impulses, while paying sarcastic attention to the details".