When Kim Philby fled to Moscow in 1963, he became the most notorious double agent in the history of espionage. Recruited into His Majesty's Secret Intelligence Service at the beginning of World War II, Philby rose rapidly through the ranks. His exposure as one of the members of the Cambridge Five--university students recruited by the Soviets in the 1930's--shocked his country. Here, Littell asks: could he really have been a triple agent, working for MI6 while supposedly spying for the Russians? A splendid Cold War spy novel by the author of The Stalin Epigram (2009).