Some weeks after the atomic bombing of Japan, Igor Gouzenko, a cipher clerk in the Soviet Embassy in Ottawa, justly fearful that he and his pregnant wife and child were about to be shipped home, packed some secret cables into his pockets, walked out of the embassy, got his small family together--and defected. His cables showed that Russia was after the bomb, named spies, and told where they were. He became the first in a wave of atom bomb spies revealed to be at work in Canada and the U.S. P.M. Mackenzie King was soon conferring with Truman in Washington, then with P.M. Clement Attlee in London; meanwhile the Soviet Embassy demanded the return of Gouzenko, stating he'd stolen funds. Hyde has interviewed his former spy-boss William ""Intrepid"" Stephenson, then chief of British security intelligence in the Western Hemisphere, and many others; gone into once-secret reports and other documents; unearthed King's unpublished diaries; and assembled a step-by-step account of the actions taken against Allan Nunn May, Donald Maclean, Klaus Fuchs, Bruno Pontecorvo, and Julius and Ethel Rosenberg--with some sidelong glances at Philby and Blunt. The Canadians, who had Gouzenko at a hideout, were forced into taking first action against the international ring, so 15 Soviet spies were arrested in one swoop--a major sensation that made headlines for a month. King appointed a Royal Commission to look into espionage and--as convictions mounted--marveled at the lack of remorse in ""these university men"" and scientists. In the States, Ethel Rosenberg was apparently arrested as an innocent lever to force Julius to confess; convicted, she sang Puccini arias to Julius in a nearby cell. Were they guilty? We won't know until the FBI releases the remaining documents in the case (not likely soon). Hyde's recountings are overstuffed with names and overweighted with material on Gouzenko; but they catch fire with schizoid Fuchs and the Rosenbergs.