German by birth, British by naturalisation, Communist by conviction, Klaus Fuchs was convicted of treason by Britain in 1950 for handing over the designs of the plutonium bomb to the Russians and has gone down in history as one of the most dangerous espionage agents in history. But, was Klaus Fuchs really evil?

Using archives long hidden in Germany and intimate correspondence, Nancy Thorndike Greenspan brings into sharp focus the moral and political ambiguity of the times in which Fuchs lived. As a university student in Germany, he resisted the Nazis and joined the Communists. After escaping to Britain, he was arrested as a German emigre-an enemy alien-and sent to an internment camp in Canada. His mentor at university, Max Born, worked to facilitate his release. When he eventually joined the atomic bomb project, first in Manhattan and later at Los Alamos, his loyalties were firmly split. In 1944, in New York with the British Scientific Mission, he started handing over research, partly because of his Communist convictions but seemingly also to level the playing field of the world powers.

Atomic Spy shows the real Klaus Fuchs-who he was, what he did, why he did it, and how he was caught. His extraordinary life is a cautionary tale about morality and the prisms through which we perceive it-and a classic anti-hero story.