FOR 400 YEARS the Queen's Messengers have carried British diplomatic pouches throughout the world. In all that time, never a lost message, a sellout, a breach. But after a strange encounter on a Mongolian railroad platform, Captain Bill Marston walks off a plane in Hong Kong. A Queen's Messenger has disappeared.

To make matters worse, the messenger carried a crucial dispatch from the mysterious "Charlie Excalibur." Even the high chiefs of British espionage do not know the real identity of Excalibur, who has been sending vital intelligence information to them for years without asking for a shilling. Now the Russians are combing Southeast Asia to kill Excalibur. He's on the run with the most fantastic piece of information he's ever collected, the reason why the United States lost the war in Vietnam. And he wants to trade it for freedom.

Only one man is qualified to locate the missing messenger. Gordon Clive has been the recipient of Excalibur's previous messages. But the last time Clive was in Thailand (where he must now go) he was captured and tortured by the enemy. He broke. He identified his compatriots, who were promptly dispatched by the Russians. Clive, who was released, vowed never to return. Ah well, what's a promise? But few willingly work with him now.

Duncan knows the Far East and the book proceeds against a lush, riveting background. Tension builds as we move from the hunted Charlie Excalibur to the haunted Gordon Clive. Clive finds the messenger but the big story is just beginning. We come upon Vietnam Vets still living in the jungle, more animal than human, a British Colonel who plays with cobras, a clownish but deadly KGB agent, a high-ranking traitor, and of course, the CIA. Throughout it all, the exquisite politeness of the Thai people contrasts well with the dark brutality of the novel.

And the danger is not only physical. Clive has left a pregnant bride back home when he runs into an ex-paramour, ready, eager, loving.

There's plenty of action, combined with a sense of deep sadness over ravaged Southeast Asia. Clive moves from the polite danger of diplomatic tea parties to a surprise ending in the jungle, where two empires play out their dreams amid the dereliction of a continent.