I would like to express special appreciation to those who graciously allowed their fictional alter egos to be flown into a desperate situation during the closing chapters. Also, I am indebted to Galen Hall and Brian Cole for their comments on an early version of the manuscript; to Major Jim Clark, U.S. Air Force (retired), and John Goff, for technical advice; to Lorna Sharp, at the Devil’s Lake Sioux reservation in North Dakota; to Christopher Schelling at HarperCollins, and Sue Warga for editorial assistance; to my wife and in-house editor, Maureen, who maintains a sense of humor about it all. And to Jim Karas, who first called Lake Agassiz to my attention.