Koko is a novel written by Peter Straub. It was first published in 1988.
Description[]
KOKO. Only four men knew what it meant. Now they must stop it. They are 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 single shattering 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, hunting someone from the past who has risen from the darkness to kill and kill and kill.