US author Shaffer planned to write the biography of Kathleen Scott, wife of the English polar explorer Robert Falcon Scott. While researching the subject, she traveled to Cambridge, England, but was discouraged to find that the subject's personal papers were nearly unusable. While dealing with this frustration, she decided to spend some of her planned stay in England by visiting Guernsey in the Channel Islands. However, as soon as she arrived, the airport was shut down due to heavy fog. She spent her visit in the airport's bookstore, reading several histories of the German occupation of those islands during World War II.
It was twenty years before Shaffer began a novel dealing with Guernsey. She had abandoned her plan to write the Scott biography, and said "All I wanted was to write a book that someone would like enough to publish."
After the manuscript had been accepted for publication (2006), the book's editor requested some changes that required substantial rewriting, but around that time Shaffer's health had deteriorated dramatically (she died on 16 February 2008). She asked the daughter of her sister Cynthia, Annie Barrows, who by that time was a well-established author of children's literature, to finish the editing and rewriting. Barrows did so, and thereby became a listed co-author on the work.