Cotton Malone retired from the high-risk world of elite operatives for the U.S. Justice Department to lead the low-key life of a rare-book dealer. But his quiet existence is shattered when he receives an anonymous e-mail: "You have something I want. You're the only person on earth who knows where to find it. Go get it. You have 72 hours. If I don't hear from you, you will be childless." His horrified ex-wife confirms that the threat is real: Their...