Eighty-year-old Lily reflects on her life starting from her early childhood. From the age of five, she longs for her mother’s love, believing that she is not worthy of it. At age six, the matchmaker Madame Wang claims Lily’s feet may be perfect after they are bound, and that with a laotong, or contracted female friendship, Lily may be eligible to marry into a family in the prosperous village of Tongkou. The next year, Lily begins her footbinding along with her cousin, Beautiful Moon, and younger sister. The process is extremely painful, and Lily’s sister, Third Sister, dies from an infection. Madame Wang visits again and says she has found a laotong match for Lily, a girl named Snow Flower from a noble family. Snow Flower writes a message to Lily on a fan in nu shu, the secret women’s language, inviting her to be her laotong. Lily replies to the message on the same fan, which they will use to write back and forth to each other for the rest of their friendship.

Lily and Snow Flower grow close over the years as they prepare for marriage, learn the domestic arts, and become adept in nu shu. One day, while sitting outside embroidering textiles for their future families, Beautiful Moon is stung by a bee and dies. Two years later, Lily marries into the affluent Lu family. After her wedding, she visits Snow Flower’s home for the first time to help Snow Flower prepare for her own marriage. However, Lily is shocked to find the home has fallen into disrepair, and that Snow Flower’s mother is dressed like a peasant. Snow Flower explains that her father had to sell their family’s land and possessions to pay for his sisters’ bride prices as he was the only son of his family. He then became addicted to opium, forcing the family into disgrace. Lily is further horrified to learn that Snow Flower will be marrying a butcher, which is seen as the dirtiest of professions. Lily insists that her feelings toward Snow Flower have not changed. However, she feels betrayed and takes her anger out on her mother for withholding the truth about Snow Flower’s family.

Over the next few years, Lily secures her place in her in-laws’ home by giving birth to two sons. Snow Flower has a son followed by two stillborn daughters, for whom she grieves. Lily and Snow Flower give birth to daughters around the same time and agree that they will be laotong. As typhoid strikes, Lily’s in-laws die, and she and her husband take on the roles of Master and Lady Lu. Once the illness subsides, Lily visits Snow Flower, though they are forced to escape to the mountains with Snow Flower’s family when a rebellion makes its way to the village. They remain in the freezing mountains for three months. After Snow Flower’s second son dies, her husband beats her until she miscarries. Depressed, Snow Flower confides in Lily how her husband mistreats her, though Lily advises Snow Flower to be obedient in order to avoid more abuse from her husband. When they are allowed to return home, Lily is thrilled to be reunited with her family. Snow Flower continues to write of her troubles, while Lily continues to implore Snow Flower to be obedient and give her husband another son.

One day, Lily receives a message from Snow Flower, saying a group of sworn sisters in her village has promised to love her, and that Lily will not have to listen to Snow Flower’s complaints anymore. Lily is furious, as she thinks this means Snow Flower has forsaken their laotong contract. She ignores other messages from Snow Flower, and rebuffs Madame Wang when she visits to begin the laotong relationship between Lily and Snow Flower’s daughters. Eventually, Lily and Snow Flower attend a Singing and Sitting Ceremony for a girl who is Lily’s neighbor and Snow Flower’s relative. Snow Flower delivers a Letter of Vituperation to Lily, explaining her sadness at Lily’s rejection of her. Lily delivers a Letter of Vituperation back, accusing Snow Flower of ending their relationship and revealing to the entire group all of Snow Flower’s secrets. Snow Flower leaves, and Lily’s Letter of Vituperation is spread throughout the county as a reminder of the importance of following cultural norms.

Eight years later, Lily has tried to forget Snow Flower. However, when Snow Flower’s daughter shows up at Lily’s house and tells Lily her mother is dying, Lily goes to her. The sworn sisters are with Snow Flower, though she mainly wants Lily’s company. Lily tries to find remedies for Snow Flower’s illness, though the sworn sisters tell her she is just making Snow Flower suffer more. Lily remains with Snow Flower until she dies. After Snow Flower is buried, Lily realizes she misread Snow Flower’s nu shu, as Snow Flower never officially became part of the sworn sisters and so did not violate their laotong relationship. Lily realizes how unfairly she treated Snow Flower, and spends the rest of her life trying to make it up to Snow Flower’s children as well as Snow Flower herself, by telling this story.