The Golden Notebook consists of alternating sections: there is a framing narrative called "Free Women," narrated in the third person and featuring a character named Anna Wulf. Anna writes in four notebooks: one black, one red, one yellow, and one blue. The novel alternates between describing Anna's life experiences and revealing the content of the different notebooks. It eventually features a section from a fifth notebook: the golden notebook.
Anna Freeman Wulf is an Englishwoman who moves to the African colony of Rhodesia in 1939, just as World War II is breaking out. During her time in Africa, she becomes involves in Leftist politics and builds a close-knit circle of friends who are also involved with the cause. Anna is involved in a romantic relationship with a man named Max Wulf but has ambivalent feelings for him throughout. As the war is ending, Max and Anna decide to have a child together; they get married in 1945, and their daughter, Janet, is born in 1946. Anna and Max get divorced when Janet is still a baby, and Anna returns to London to live as a single mother and work as a writer. In 1951, Anna publishes a novel called Frontiers of War, which is set in Africa. The novel draws on her own experiences and ends up selling very well, giving Anna enough money to live off of. Anna also becomes active in working for the British Communist Party.
Upon her return to England, Anna ends up living with a woman named Molly, who is also a single mother. Molly has been raising her son, Tommy, after getting divorced from her husband, Richard. Anna also becomes romantically involved with a married man named Michael, whom she loves very much and has a five-year relationship with. In 1954, Anna's relationship with Michael ends, and she also leaves the Communist Party after growing increasingly disillusioned. The frame narrative opens in 1957, with all of these past events gradually being revealed through the contents of the notebooks. The black notebook focuses on Anna's experiences in Africa and her experiences with the reception and adaptation of her novel. The red notebook focuses on her experiences with Communism, while the yellow notebook contains a narrative called "The Shadow of a Third," which seems to be a thinly fictionalized account of Anna's relationship with Michael. The blue notebook resembles a journal, in which Anna records memories and reflections.
In 1957, Anna is trying to help Molly and Richard with their adolescent son, Tommy. Unfortunately, Tommy attempts to commit suicide and is left blind as a result. The suicide attempt and Tommy's subsequent strange behavior prompt Anna to reflect on her life and her purpose in writing. She is feeling anxious about writing a second novel, but she is unsure of how to proceed. By the time Tommy recovers, Anna's own mental health is becoming increasingly disturbed. After her daughter goes to boarding school and Anna is left alone, she becomes involved in a destructive affair with an American screenwriter. This relationship pushes Anna to the brink of a mental breakdown, but this results in her eventually being able to begin her second novel. The scene in which she writes the first line of that novel reveals that the frame narrative itself is also a larger piece of fiction, written by Anna herself.
Anna eventually decides that she needs to find work, and the novel ends with her telling Molly about her plans to work as a marriage counselor and teacher. By this point, Molly is planning to remarry. The novel ends with the two women calmly going about their everyday lives.