In 1944, 13-year-old Fritz Tubach was almost old enough to join the Hitler Youth in his German village of Kleinheubach. That same year in Tab, Hungary, 12-year-old Bernie Rosner was loaded onto a train with the rest of the village’s Jewish inhabitants and taken to Auschwitz, where his whole family was murdered. Many years later, after enjoying successful lives in California, they met, became friends, and decided to share their intimate story—that of two boys trapped in evil and destructive...