Murder on the Danube — William S. Shepard

Robbie Cutler, American Embassy political officer in Budapest, must solve a ghastly sabre murder before the Mafia murders him. The clue lies in finding out which person betrayed his group of Freedom Fighters in the 1956 Hungarian Revolution. But they were all patriots, weren't they? The answer involves sorting through the past, finding the traitor, and unearthing a special love story, deepened by conflict against hopeless odds.