Kazuko, a divorced, childless woman of twenty-nine, lives with her mother in a small cottage in the mountains of Izu, on the Pacific coast of Japan. Although their family was once aristocratic, they are now poor and are forced to sell their possessions to survive. After the death of Kazuko’s father, she and her mother were forced to move to Izu.

One day, Kazuko finds snake eggs in the garden and burns them. Her mother disapproves of her choice, believing that she has brought bad luck to them by doing so. Shortly after, Kazuko accidentally sets a fire and is forced to apologize to their neighbors; some are more forgiving than others. The following day, Kazuko begins working in the fields as a peasant, which reminds her of when she was conscripted to work for the war effort years earlier.

Naoji, Kazuko’s brother, was in the army in the South Pacific and has been declared missing. While their mother believes him dead, Naoji eventually turns up, returning to Japan to live with his mother and sister in Izu. However, he returns home with an opium addiction and a penchant for spending money, exacerbating the family’s already dire financial situation. Kazuko writes to Naoji’s friend and teacher, the novelist Mr. Uehara, whom she met years ago. She asks him to accept her as his mistress and have a child with her, but he never answers her letters. Kazuko’s desperation and despondency increase, as she can neither endure her situation nor see any escape.

Kazuko plans to travel to Tokyo and visit Mr. Uehara in person, but just before she leaves, her mother falls ill with tuberculosis. One day, her mother tells her that she dreamed about a snake in front of the house and asks Kazuko to see if it is there. Kazuko sees the snake and finally accepts that her mother is going to die, which she does soon afterward. Her last words are an expression of concern for how hard Kazuko must work to survive. 

Kazuko feels ashamed that such a gentle and beautiful person as her mother cannot continue to exist in a world where she must fight for survival. Soon after her mother’s death, she goes to Tokyo and finds Mr. Uehara. Though he is much changed and seems close to death, she finds that she still loves him. The two of them share a bed, talking nihilistically about the emptiness of life. On the following morning, Naoji commits suicide.

Naoji left a note for Kazuko, in which he says that he can see no reason to go on living. Life has always been painful for him, which is why he became addicted to opium. He has tried to renounce his aristocratic background but failed to do so and is now equally ill at ease among aristocrats and working people. He adds that he is in love with a woman called Suga but has never declared his love and only mentions it now so that Kazuko will understand how he has suffered. He knows that he has caused her pain and has decided to kill himself while she is in Tokyo so that she will not be the one who discovers his body. 

A month after Naoji’s death, Kazuko writes to Mr. Uehara to tell him that she is pregnant with his child. She does not ask him for help or to abandon his unhealthy lifestyle, as she feels prepared to fight her battle against conventional morality alone. However, she hopes that one day, even if only once, his wife will take their child in her arms, seeing Mrs. Uehara as a stand-in for her own mother.