What does Claudia describe as her "core story" in the novel, Moon Tiger?

The story of Claudia and Tom, which Claudia describes as her “core story,” takes place in Egypt during World War II. Claudia has come to Egypt as a war correspondent, and Tom is a British military officer. The desert and Cairo are both described at length in the novel and function almost as characters. Soon after meeting in the desert, Claudia asks Tom to describe his time there. We do not his full account of the desert until the penultimate chapter, when we read the diary in which he attempted to answer Claudia’s question. Soon after meeting, Tom and Claudia walk around Cairo. We also see Cairo in Claudia’s memory of going to pray for Tom after learning he has been listed as missing. Claudia leaves the cathedral and walks along the Nile, feeling the life and vibrancy of the city is an affront to her pain. Claudia returns to Egypt as a tourist in her old age and finds it very much changed. Its modernization, however, does not erase for Claudia the poignancy of her memories there.