The black notebook resumes with content in both the "Source" and "Money" columns. The Source column picks up in 1955 with an entry describing a London man kicking and killing a pigeon and then being confronted by a woman who has witnessed the act. The description may be a dream since the next entry mentions Anna having dreamed of a pigeon and recalling a day in Africa when Mrs. Boothby asks the group if they can go and shoot some pigeons so that she can make pigeon pie for her husband. Paul, Jimmy, Willi, Anna, and Maryrose all venture out, becoming distracted by watching large groups of butterflies and grasshoppers. Paul shoots and kills some pigeons, although all of the others find the process of watching to be distressing in different ways.
Under the heading "Money," Anna describes receiving a request for either stories or portions of a journal. She refuses, but records a number of fictional journal entries from the perspective of a young American writer, describing his life of pretentious debauchery in Europe. She shows this journal to an American writer named James Schafter, who finds it hilarious. Together, Anna and James craft another series of fictional journal entries written from the perspective of a woman writer who has lived in Africa. The entries describe a woman who has written a novel called the Frontiers of War and is considering adapting it into a play. She discusses the adaptation with her friend Harry, who suggests altering the love story into an account of a white man being falsely accused of rape by a young African woman. The narrative then shifts to a short story written by James called "Blood on the Banana Leaves," featuring a love story between a white man and an African woman; after she is raped, he kills another white man in revenge. The notebook then shifts to a series of reviews of Anna's novel, all published in Soviet journals.
The narrative shifts to the red notebook with a series of entries from 1955-56. The entries describe Anna's growing disillusionment with the British Communist Party. The entries end with Anna describing how Molly has told her that Tommy has become active with a socialist party. Molly is astonished that Tommy seems to be focusing on the same ideas that had once inspired her and Anna, and she expresses her wonderment that the new generation does not know any better. Anna consoles her friend by explaining that it is better for Tommy to become focused on socialism rather than on his own personal success and monetary gain. The narrative then shifts to the yellow notebook; after the end of her relationship with Paul, Ella moves into a new flat, which annoys Julia. Dr. West, who contributes a medical column to the magazine Ella works at, tries to pursue her, but she turns him down; he ends up having an affair with Ella's editor instead. The experience of talking with Julia about Dr. West's overtures brings the two women closer again as they complain about men, but Ella also feels worried that her friendship with Julia is reliant on both women disliking and distrusting men.
A short time later, Ella begins having an affair with Jack, a married man with whom she works at the magazine. She is beginning to doubt whether her approach to sexuality is bringing her happiness or pleasure, but she doesn't know what else to do. She has another unsatisfying sexual encounter, this time with a married Canadian screenwriter whom she meets at a party. Afterward, she resolves to give up men and focus on her writing. The narrative is interrupted by Anna's voice, musing on the experience of writing about a character named Ella. Then, the narrative resumes from Ella's point of view, with her contemplating different ideas for her second novel. She goes to visit her father and asks about his relationship with her mother, now long dead. Ella's father explains that his wife disliked sex, so he sought other sexual partners even though he knew this made his wife jealous and unhappy. Before the visit ends, Ella asks her father if he has ever written poetry, and he admits that he has.
By this point, the content of the notebooks has become fragmentary and more confusing, moving fluidly between different sections and often leaving the reader unclear as to exactly what can be trusted. Anna seems to have grown increasingly disconnected from her former Communist beliefs, but this loss of an overarching worldview leaves her without anything firm to believe in. Molly seems to see Communist beliefs as old-fashioned and out of step with modern times; she is baffled as to why her son would be interested in exploring this ideology.
Anna's inability to find a stable and satisfying political worldview is echoed by Ella's inability to find a satisfying romantic relationship. She has no trouble meeting men who are attracted to her, but none of them seem to be single. Interestingly, Ella never questions whether it is her choice of married men as sexual partners which is setting her up for failure, nor does she seem to feel guilty about these relationships. The root of her unease seems to be a realization that she will only find sexual fulfillment when she also feels an emotional connection to a partner, paired with the knowledge that she lives as though she dislikes men while actually craves a consistent male presence in her life. Ella's conversation with her father suggests that she likely did not grow up watching a happy marriage. Psychoanalytic theory would argue that childhood trauma can permanently impact someone's development, so Lessing may be hinting that Ella is doomed to repeat the unhappiness of her parents' marriage.
Ella's father also offers a window into an earlier generation where many similar problems arose but were handled differently. Not unlike Ella, Anna, Richard, and the various other post-war characters, Ella's father struggled with finding sexual fulfillment within the confines of a marriage. He, however, chose to simply maintain a double life, and it didn't seem to occur to him to try to achieve the unified happiness which the other characters seek. The revelation that he also wrote poetry suggests he also went through a similar process where his vocation was concerned. A more modern character like Tommy can think about what role he wants art to play in his life and agonize over choosing a life path. Ella's father simply compartmentalized part of himself and hid away what was complicated. His secrecy mirrors the way in which Anna seems to want to keep some pieces of her identity neatly hidden away.
Nonetheless, in this section, Anna deliberately breaks the illusion of the yellow notebook and treats it as metafiction, a place where the voice of the writer breaks in to reflect on the process of writing and composing. Ella's narrative is a storyline where Anna can displace feelings and experiences she is uncomfortable writing about in the first person, but she also explicitly reflects on her choice to do so. The title "Shadow of a Third" seems to have primarily referred to Paul's wife, and her impact on the relationship between Paul and Ella, but it might also hint at Anna as a kind of "third" who hovers over the narrative and occasionally breaks in to speak explicitly.
This play of narratives set within narratives and confusion over different voices is most vivid in this section of the black notebook. Anna purposefully ventriloquizes different voices, writing in personas that are either radically different (a young American playboy) or confusingly similar (an Englishwoman who has written a successful novel about Africa). She also inserts voices of other writers and reviews as ways of decentering her own voice and leaving the reader off-balance, unsure of what is fact and what is fiction. This increasingly confusing and fragmented narrative signals Anna's own increasing inability to remain in control of her thoughts and feelings.