More than most of us, Mary Palevsky needed to come to terms with the moral complexities of the atomic bomb: Her parents worked on its development during World War II and were profoundly changed by that experience. After they died, unanswered questions sent their daughter on a search for understanding. This compelling, sometimes heart-wrenching chronicle is the story of that quest. It takes her, and us, on a journey into the minds, memories, and emotions of the bomb builders.

Scientists Hans Bethe, Edward Teller, Joseph Rotblat, Herbert York, Philip Morrison, and Robert Wilson, and...