On the 29th of August 1949, the USSR set off their first atomic bomb, just four years after the Americans. The speed with which they achieved this surprised the world. What nobody knew was that it was the result of espionage implemented at the heart of the United States. At the centre of the operation was a very unusual female spy, Elizabeth Zaroubin. She managed to gain the confidence of great researchers such as Einstein, in a story worthy of the best spy novels ever written.