The Kremlin Armoury

David Marriner, the hero of this slow- paced but unusual thriller, is a museum specialist whose wife wants a di vorce--and custody of their daughter. When British intelligence offers him the services of the top divorce lawyer in London, Marriner decides to partici pate in an elaborate plan to help a strategically placed Soviet defect. First, he accepts an invitation to visit Svetlana Malinkova, director of the fa mous Kremlin Armoury Museum, whom he has just met. Malinkova agrees to help with the plan, but she wants to defect as well, and to bring her impressive collection of purloined art with her. Desperate to hang on to his daughter, Marriner is drawn deeper and deeper into a complex web. Just as his domestic situation begins to show promise, he must return to Moscow to carry out the increasingly dangerous mission, which ultimately forces him to risk his freedom, his career and the lives of the people he loves most. The ending, while unexpected, stretches credibility, but this thriller has an add ed dimension most such books lack, because its protagonist is driven by personal problems rather than by the typical secret agent code. Hunter, a Londoner, is the author of the paper back original Comrades. (Aug.)