Claudia Hampton, a 76-year-old English woman and a professional historian, is terminally ill and is spending her last remaining moments in and out of consciousness thinking of writing a history of the world with her life as a blueprint. Her first, primordial recollections are of a father that died in World War I, and of the summer of 1920, when she was 10 and competing with her 11-year-old brother Gordon for fossils.
Claudia and Gordon are, at times throughout their lives, rivals, lovers, and best friends to each other. When the two are in their late teens they begin an incestuous relationship and find it hard to relate to almost any other person their own age. Soon, however, their college careers and other events allow both to open up to the outside world, and look outward for companionship.
At the outset of World War II, Gordon, a would-be economist, is sent to India, whereas Claudia sets aside her studies in history to become a war correspondent. Independent and enterprising, Claudia talks her way into a correspondent's post in Cairo, where she meets Tom Southern, a captain of an English armoured tank division, who sweeps her off her feet.
Tom and Claudia spend a long weekend together while he is on leave from the front, which culminates in both of them falling in love with each other and making plans for a seemingly far future. But their future together is never to materialize: shortly after their time together, the English are called to defend Egypt from Erwin Rommel's offensive at the First Battle of El Alamein, and Tom is declared missing. Later on, Claudia receives news that he has died.
Shortly after Tom's death, Claudia finds out she is pregnant, and decides that she will have the child, even though she would have to raise it alone. It isn't to be: Claudia miscarries, and is never told whether the child she had carried was a boy or a girl. That uncertainty, along with her fear that Tom died a horrible and painful death, will haunt her for the rest of her life.
After the War, Claudia and Gordon reunite, but the encounter is more friendly than passionate. Each of them has obviously been changed by the War, but they are both sparse on actual details during their conversations. Gordon marries a girl named Sylvia, who Claudia finds insipid and boring. Claudia meanwhile met Jasper, a well connected young man who she goes on to have an on and off, rather stormy relationship with, and one that Gordon is openly disapproving of.
In 1948 Claudia finds herself pregnant again, this time by Jasper, and while she has no intention of marrying him, she decides to have the child, Lisa. While Claudia loves Lisa, she finds she has little patience and time to care for a child, and so Lisa ultimately ends up being raised by her maternal and paternal grandmothers, who share her custody and dictate her upbringing. Not surprisingly, Lisa grows up sullen and indifferent to Claudia, and marries off at a young age to a respectable (boring) man.
Throughout her travels abroad, Claudia comes in contact with an Hungarian functionary who becomes implicated in the 1956 Hungarian Revolution. Knowing that persecution is forthcoming, the functionary decides to ask Claudia to make sure that his son Laszlo, who is in England at college, does not attempt to return to Hungary. So Claudia becomes a sort of surrogate mother to Laszlo, who she grows to love and admire over the years, recognizing that he is drastically different from anyone else she knows: an open, painfully honest, sensitive, self-destructive artist.
Claudia writes several books that attempt to popularize history for the masses, earning her accolades from the public, and scorn from other professional historians. She also briefly becomes a consultant for a movie based on her history of Cortez, which leads to a personal scandal, when she ends up in a car accident with the star of the movie, and the press suspects there is more to the relationship than just friendship. The event earns scorn from Jasper, who refuses to see her when she is in the hospital. Gordon, on the other hand, visits her to let her know that she is not alone.
At some point in time, Claudia decides to travel to Egypt alone, to try to see Cairo again, but she finds things much changed. The only thing that has not changed is that the desert has become forever etched in her memory as synonymous with her pain at everything she experienced during the war, a pain that she is still unable to share with any other living soul even after all the years that have passed.
When Claudia turns 70, she receives a package containing Tom's diary, one of the few personal effects of Tom's recovered from the war. It had been sent to Claudia by Jennifer Southern, Tom's sister, who decides that Claudia should have it upon realizing that Claudia is "C.", Tom's often referred to girlfriend. Claudia cannot muster the courage to read beyond the note accompanying the diary, and so sets the book aside.
Shortly thereafter, Gordon dies, and leaves a gaping void in Claudia's life. A few years later, when she is diagnosed with cancer, and knowing death is imminent, she tries to tentatively reach out to Lisa, to apologize for having been a cold and distant mother. Lisa accepts the apology, but is not sure how to feel about it: it is the most unlikely thing Claudia (who to Lisa seemed to revel being an almost omnipotent figure), has ever done for Lisa.
Right before dying, Claudia finally musters the courage to ask Laszlo to fetch her Tom's diary. Poring over the short entries in the diary, Claudia allows herself to reflect on her bitterness about having been left behind and having become wholly different from the woman he knew and loved, and to make peace with the fact that she too will soon become nothing more than a set of imperfect memories as recalled by those who knew her. The next day, Claudia passes away.