This riveting love story, revolving around two extraordinary individuals, plays out against some of the most profound markers of the 20th century: Hitler's Germany, the American immigrant experience and growing threats of the nuclear age. Hermann Hoerlin and Kate Tietz Schmid meet in 1934; he, a handsome world record-holding mountaineer and aspiring physicist, is a staunch anti-fascist and she, part of Munich's intellectual and musical elite, is a stunning widow whose husband was murdered by the Nazis. To have a future together, Hoerlin (as she called him) and Kate must flee Germany. Standing in their way is a major obstacle, the Nuremberg Laws, prohibiting relationships between Aryans and Jews.

Against formidable odds and with the direct assistance of a few 'good' Nazis, Kate and Hoerlin manage to marry and immigrate to the United States. However, as "enemy aliens" during World War II, they face new adversities. Life finally returns to normal with the help of influential friends, including a connection with Eleanor Roosevelt. And, in a strange twist, Hoerlin contributes to the war effort with his extensive European mountaineering maps that help guide Allied reconnaissance missions. In 1953, Hoerlin and Kate pull up stakes again, moving to the Atomic City of Los Alamos where Hoerlin works at the forefront of the first nuclear test ban treaty. Again, he is brought under scrutiny, this time because of McCarthyism and Hoerlin's links with the American left-wing.

The book spans an era from the rise of Nazism, when a diabolic dictator sets out to annihilate Jews, to the depths of the Cold War, when weapons of mass destruction threaten to annihilate humankind. In their remarkable odyssey, Kate and Hoerlin befriend cultural and scientific icons such as the philosopher Oswald Spengler, cellist Pablo Casals, conductor Wilhelm Furtwangeler, painter Georgia O'Keefe and Nobel prize-winning physicist Hans Bethe. Their daughter, Bettina Hoerlin, draws on a treasure trove of over 500 love letters and previously untapped archival records to create a universal tale of courage.