On the afternoon of Feb. 10, 1933, in the north German city of Kiel, a bespectacled math prodigy was lifted off his feet by a crowd of Nazi Brownshirts and tossed into the freezing waters of the Baltic Sea. Left for dead, he somehow swam to safety. His name was Klaus Fuchs. Until then he had been a socialist who had joined the local Communist Party only as a last resort, to do more in the fight against Nazism. But this political baptism altered his outlook. It was the starting point in an explosive chain reaction—akin to the atomic chain reactions he would soon be studying in his pioneering work as a scientist—that would lead to Klaus Fuchs being described by the U.S. Congress, in 1951, as a man who “influenced the safety of more people and accomplished greater damage than any other spy not only in the history of the United States but in the history of nations.”
