Shin, a nobleman, had been trying to conceive a male heir to pass his family name. Unable to provide a male heir, Shin's wife gives her husband permission to search for a surrogate wife to bear a male heir.On the way to finding a surrogate wife, Shin runs into a 17 year old girl, Ok-nyo (Kang Soo-yeon). She was a poor feisty girl who stated she would do anything for money. The stubborn nature of Ok-nyo attracts Shin and influences him to choose her to become the surrogate mother for his child. Ok-nyo holds the social status of a servant, but the relationship changes both of them through the course of the movie. Ok-nyo had to obey rules which keep her hidden during the day and delegated her to perform the mating ritual during Shins wife's hours of choosing. No matter what was happening, Ok-nyo could not leave the building in which she was housed. With Shin's infatuation and Ok-nyo's attachment, both secretly meet for passionate affairs. Unfortunately both eventually get caught, which causes their separation. Ok-nyo's mother tries to dissuade her to break off the relationship by telling her the realities of life. Even though both were punished for the incursion, they still meet until the end. Eventually Ok-nyo conceives the child heir for Shin and is burdened with the mystery of whether Shin will stay by her side or leave with her child forever.