Masako, a housewife working night shifts at a bento factory, is tired of her cold and conversationless family life. Her only pleasure is talking about trivial things with her colleagues from the factory, who are each shouldering their own burden, and a female detective, Noriko, whom she met due to a certain event.

One day, Yayoi, Masako's work colleague, consults her, saying that she has killed her violent, gambling-addicted husband. Masako and her workmates, Yoshie and Kuniko, are dragged into a heinous crime, involving the dismemberment and disposal of Yayoi's husband's body.