Traitor's Kiss

Officially the Cold War is over and the hand of friendship has been exchanged in public. In private though the intelligence war continues. A British trawler strays into Russian waters. On its return the captain has a package for British Intelligence. For the next four years a high-ranking Russian naval officer provides MI6 with priceless information. But suddenly he goes quiet. Clearly under suspicion the decision is made to get him out. But his controllers in London know nothing about him ?