The Cry of the Halidon by Robert Ludlum

Alex McAuliff has received an offer he can’t refuse: two million dollars for a geological survey of Jamaica. All Dunstone Limited requires is his time, his expertise, and his absolute secrecy. No one—not even McAuliff’s handpicked team—can know of Dunstone’s involvement. But British Intelligence is aware of the deal, and they’ve let Alex in on a secret of their own: The last survey team Dunstone dispatched to Jamaica vanished without a trace. Now it’s too late to turn back. Alex already knows about Dunstone—which means he knows too much. From the moment he lands in Jamaica, Alex is a marked man. On an island paradise where a beautiful woman might be a spy and every move could be his last, Alex’s only clue to survival is a single mysterious word: Halidon.