Stefanie von Hohenlohe was born to a middle-class Viennese family and of partly Jewish descent. After marrying and divorcing a German prince, she became a close confidante of Hitler, Göring, Himmler (who declared her an "honorary Aryan"), and von Ribbentrop. After arriving in London in 1932, she moved in the most exclusive circles, arranging the visits of the Duke and Duchess of Windsor and Lord Halifax to Germany in 1937. Most notoriously, she was paid a retainer of £5,000 per year by Lord Rothermere, owner of the Daily Mail and the Daily Mirror and an open supporter of the Nazi regime. In 1939 she fled to the U.S.; a memo to President Roosevelt described her as a spy "more dangerous than ten thousand men." This new biography uses recently declassified MI5 files and FBI memos to examine what motivated both Stefanie and Rothermere, shedding light on the murky goings-on behind the scenes in Britain, Germany, and the U.S. before and during World War II.