After a chance meeting in 1981, Lily Fialka confronts the defining time of her life: 1943–45 in Los Alamos, when her physicist husband, Peter, worked on the atomic bomb as part of the Manhattan Project—a time of isolation, hard work, temptation, and loneliness, yet exhilaration and triumph; when great breakthroughs were made, but lives felt narrow; when loyalty was paramount, but the need for secrecy created unbearable tension. At the same time, Lily and her friends are haunted by what is happening to Dietrich Bonhoeffer in the Resistance in Germany, and his story serves as a counterpoint to theirs. In a sweeping historical novel that cuts across continents and reveals a deep knowledge of the science of the making of the bomb, offers valuable insights into that fascinating time.