WASHINGTON — One lazy, sultry afternoon in 1947, two years after America helped trounce the Nazis, my father arrived at our family’s modest summer house on the Severn River near the Naval Academy. He had come from his job as a police detective in D.C., still wearing his suit and his service revolver. “Get your shoes on and come with me,” he told my 10-year-old brother, Martin, his Irish lilt edged with a steel that caused his son to scramble. “I have something to do and I want you to see it.” The town, Herald Harbor, Md., had its share...