As much as possible, I tried to visit or experience the places and things that I write about in the book. Paris was easy enough, and there I visited Notre-Dame, Saint Sulpice and the Catacombs where significant scenes take place. The Brittany area however, I have not seen yet, nor the Caverns of Raoul, except in pictures. At the beginning of the book, Jacob parachutes out of a modified B-24 so I thought I should take a spin in the one flown by the Collings Foundation. I also visited the Café Sussex, which is no more, but a plaque commemorates the daring work done there.

    For all other research, I relied on great books like Code Name Christiane Clouet about a young woman in the Resistance, Suite Française by Irène Némirovsky, to give me a sense of place, and Is Paris Burning to maintain historical accuracy during the rapid developments during the Liberation.