In 1942, in an English Cotswolds village, Ursula Burton lived a quiet life with her husband and three children. Behind the facade, Burton was a dedicated Communist, a Soviet colonel, and a veteran agent—code-named Sonya—gathering the scientific secrets that would enable the Soviet Union to build the bomb. With unparalleled access to Sonya's diaries and correspondence, Ben Macintyre tells the story of a legendary spy who evaded the Nazis, the FBI, and MI6, and helped plunge the world into a decades-long standoff between nuclear superpowers.

"Macintyre writes with the diligence and insight of a journalist, and the panache of a born storyteller."—John Banville