Max Bretzfeld doesn’t want to move to London. Leaving home is hard and Max is alone for the first time in his life. But not for long. Max is surprised to discover that he’s been joined by two unexpected traveling companions, one on each shoulder, a kobold and a dybbuk named Berg and Stein. Germany is becoming more and more dangerous for Jewish families, but Max is determined to find a way back home, and back to his parents. He has a plan to return to Berlin. It merely involves accomplishing the impossible - becoming a British spy.

Max Bretzfeld's dangerous mission begins when he returns home to Berlin as a British spy in the much-anticipated second book in Adam Gidwitz's duology that began with Max in the House of Spies. Max was on a mission. Well, two missions. One mission his British spymasters knew about: infiltrating the Funkhaus, the center of Nazi radio and propaganda. The other, they did not: finding his parents. Max Bretzfeld was willing to do anything to return to Germany, even become a British spy. Training complete and forged papers in hand, the radio wunderkind’s mission has begun—gain access to the legendary Funkhaus, the base of operations for the Ministry of Propaganda and Popular Enlightenment headed by Joseph Goebbels.