Writer Rebecca Donner was a teenager when her grandmother thrust a fistful of old letters into her hands and said, One day you must tell Mildred’s story. Mildred Harnack is Rebecca Donner’s great-great-aunt: the only American in the leadership of the German resistance in Berlin. A born-and-bred Midwesterner hailing from Milwaukee, Mildred Harnack was a young American expat pursuing her PhD in early-1930s Berlin when she began recruiting Germans into the underground resistance.