In the quiet Cotswolds village of Great Rollright in 1944, a thin, and unusually elegant, housewife emerged from her cottage to go on her usual bike ride. A devoted mother-of-three, attentive wife and friendly neighbour, Sonya Burton seemed to epitomise rural British domesticity. However, rather than pedalling towards the shops with her ration book, Sonya was heading for the Oxfordshire countryside to gather scientific secrets from a nuclear physicist. Secrets that would enable the Soviet Union to build the atomic bomb. Far from an obedient homemaker, Sonya Burton was a dedicated communist, a decorated colonel and a veteran spy who risked her life to keep the Soviet Union in the nuclear arms race. In Mrs Burton, Ben Macintyre reveals the astonishing story behind the most important female spy in history.