Pavel, a KGB double agent, defects in Helsinki during the detente talks, taking with him enough rough diamonds from Russian mines to upset the world's diamond market. What's more, he has ""secret"" papers planted on him proving that the USSR--which owns more diamonds than the total carat value of the Free World--is going to follow his play and unload its stones also. The UK decides it doesn't want this particular defector, even if he is a KGB officer, and assigns British intelligence agent Calder to get Pavel aboard an Illyushin jet back to Moscow. High-level news leaks plunge the market into disaster. Meanwhile, the defector escapes and pursues Calder's girl, herself a defector. She falls for him--but it's the Third Man theme as the bittersweet lovers part and Pavel boards the Moscow-bound jet as a KGB prisoner. Calder gets nothing. Strong characterizations, authentic talk, and intriguing despite a high fantasy quotient, money sprees, hit men with dart guns. . . .