Book excerpt: From the #1 New York Times bestselling author of Ghost Story comes “an inspired thriller” (The Washington Post) about four Vietnam vets linked by a shattering secret and their global hunt to track down a brutal killer. Koko. Only four men knew what it meant. Now they must stop it. They were Vietnam vets—a doctor, a lawyer, a working stiff, and a writer. Very different from each other, they are nonetheless linked by a shared history and a devastating secret. Now, they have been reunited and are about to embark on a quest that will take them from Washington, D.C., to the graveyards and fleshpots of the Far East to the human jungle of New York, searching for someone from the past who has risen from the darkness to kill and kill and kill.