[2] The film is about the story of Kim Ji-young, a woman in her 30s who starts acting strangely, seemingly possessed by her mother and late grandmother after becoming a stay at home mom.

She is a stay-at-home mom whose main responsibility is raising her daughter whilst her husband, Daehyun(Gong Yoo) works a day job at an office.

Due to all these, Jiyoung unknowingly started to develop a mental disorder which consists of her seemingly becoming briefly possessed by the personality of her mother or late grandmother.

He encourages Jiyoung to return to work and says that he will take parental leave for a year and become a stay-at-home father and take over the responsibility of raising their daughter.

One day, Jiyoung finally confronts Daehyun about his insistent urge for her to seek professional counselling as she is still personally unaware of her possession.

As well as the overall discrimination women in the workplace have suffered as they are deemed less competent than their male colleagues, Jiyoung is also mocked by her juniors as they view her as a freeloader scrounging off her husband.

Emboldened by these psychiatric sessions, Jiyoung becomes more outspoken in public, speaking up for herself when she hears her colleagues talking bad about her behind her back.

Eventually, she also starts writing opinion pieces and personal accounts for magazines, and voicing concerns about issues that mothers and women face in South Korea.

As Jiyoung becomes happier and healthier, the movie ends with her sitting down at a desk and starting the first line of her self-titled memoir, implying that she has also decided to become an author.

[3] While adapting the novel into a film, Kim's "biggest task was to weave the series of independent episodes in the original material into a story with a central narrative.

[5] On October 17, Gong Yoo was confirmed to play Kim Ji-young's husband, starring for the third time alongside Jung Yu-mi after Silenced (2011) and Train to Busan (2016).