Her book traces the lives of the three Himmler brothers (the eldest was Gebhard Himmler), the sons of a respected secondary school headmaster in Munich. Gebhard served in the German Army in World War I, but Heinrich, who at 18 was still an officer cadet when the war ended, was too young to see frontline service. Katrin Himmler speculates that it was frustration at this and envy of his brother that led Heinrich to join the extreme right-wing Freikorps in 1919. In the Freikorps he served under Ernst Röhm and was thus led into the Nazi Party.