A word about time travel. While it is true that quantum teleportation has been demonstrated in laboratories around the world, the practical application of such phenomena lies in the future. The ideas presented in this book were stimulated by the speculations of David Deutsch, Kip Thorne, Paul Nahin and Charles Bennett, among others. What appears here may amuse them, but they would not take it seriously. This is a novel: time travel rests firmly in the realm of fantasy.
But the representation of the medieval world has a more substantial basis, and for it I am indebted to the work of many scholars, some of whom are identified in the bibliography that follows. Errors are mine, not theirs.
I’m grateful as well to Catherine Kanner for the illustrations, and to Brant Gordon for the computer-generated architectural renderings.
Finally, my particular thanks to historian Bart Vranken for his invaluable insights, and for his companionship while tramping through little-known and neglected ruins of the Périgord.