London was a very dangerous place to live during World War II, and many children were evacuated to Ireland or the United States. Only child Elizabeth White is sent to live with her mother's childhood friend and her large and bustling family, the O'Connors, in Ireland. Although the mothers were childhood friends, their relationship has become one-sided with Elizabeth's mother, Violet, rarely corresponding and Aisling's mother, Eileen, remembering their closeness with detailed letters. Violet believes even though Ireland is not as refined as her London, it is a safe place for her daughter.
Elizabeth quickly becomes fast friends with Aisling, who is the same age. The story follows these two girls, along with the whole O'Connor family, as they grow into teenagers and young women. Aisling is outgoing and bold, while Elizabeth is quiet with all the manners of a well-bred child. Elizabeth is shown a caring, loving family and begins to feel part of a real family, as opposed to the cold environment of her parents' house.
After the war ends, Elizabeth goes back to London, leaving behind a loving family and returns to the quietness of her real family. The two girls have formed a bond that remains, however, for years after the war is over. They remain in close contact through letters, supporting each other through their marriages. Their lives remain intertwined, each facing her own relationships, successes, and failures.