First and foremost, to my friend and editor, Jason Kaufman, for working so hard on this project and for truly understanding what this book is all about. And to the incomparable Heide Lange—tireless champion of The Da Vinci Code, agent extraordinaire, and trusted friend.

I cannot fully express my gratitude to the exceptional team at Doubleday, for their generosity, faith, and superb guidance. Thank you especially to Bill Thomas and Steve Rubin, who believed in this book from the start. My thanks also to the initial core of early in-house supporters, headed by Michael Palgon, Suzanne Herz, Janelle Moburg, Jackie Everly, and Adrienne Sparks, as well as to the talented people of Doubleday's sales force.

For their generous assistance in the research of the book, I would like to acknowledge the Louvre Museum, the French Ministry of Culture, Project Gutenberg, Bibliothèque Nationale, the Gnostic Society Library, the Department of Paintings Study and Documentation Service at the Louvre, Catholic World News, Royal Observatory Greenwich, London Record Society, the Muniment Collection at Westminster Abbey, John Pike and the Federation of American Scientists, and the five members of Opus Dei (three active, two former) who recounted their stories, both positive and negative, regarding their experiences inside Opus Dei.

My gratitude also to Water Street Bookstore for tracking down so many of my research books, my father Richard Brown—mathematics teacher and author—for his assistance with the Divine Proportion and the Fibonacci Sequence, Stan Planton, Sylvie Baudeloque, Peter McGuigan, Francis McInerney, Margie Wachtel, André Vernet, Ken Kelleher at Anchorball Web Media, Cara Sottak, Karyn Popham, Esther Sung, Miriam Abramowitz, William Tunstall-Pedoe, and Griffin Wooden Brown.

And finally, in a novel drawing so heavily on the sacred feminine, I would be remiss if I did not mention the two extraordinary women who have touched my life. First, my mother, Connie Brown—fellow scribe, nurturer, musician, and role model. And my wife, Blythe—art historian, painter, front-line editor, and without a doubt the most astonishingly talented woman I have ever known.