From planning an assassination attempt on Hitler in Switzerland, to spying on the Japanese in Manchuria, to preventing nuclear war (or so she believed) by stealing the science of atomic weaponry from Britain to give to Moscow, Ursula Kuczynski Burton conducted some of the most dangerous espionage operations of the twentieth century. Born to a German Jewish family, as Ursula grew, so did the Nazis' power. A fanatical opponent of the fascism that ravaged her homeland, she was drawn to communism as a young woman, motivated by the promise of a fair and peaceful society. She eventually became a spymaster, saboteur, bomb-maker and secret agent. In Agent Sonya, Britain's most acclaimed historian vividly reveals the fascinating tale of a life that would change the course of history. Classic Ben Macintyre - a gripping ride, based on meticulous research, that reads like a novel - this is the greatest spy story never told.