Dan Grunfeld: When my grandmother was 18 years old, a short letter from her father saved her life. Scribbled hastily in swooping cursive, it read, “If you can, stay where you are.” It was the last time she would ever hear from her beloved father. Shortly thereafter, Nazis rounded up the rest of her family from their village in rural Romania and sent them to Auschwitz. My grandmother was visiting her sister in Budapest and had a chance to survive on the run.