One day, soon after we moved to the city, I was at home still unpacking cartons when the doorbell rang. I opened the door to a young woman about my age. “Welcome to the building,” Celia said introducing herself. “I’m baking and I’ve just run out of sugar. May I borrow a cup?” I invited her in and over tea we discovered that Celia and my husband grew up in the same Queens neighborhood, and had gone to Brandeis together where they had been friends — small...