Patty and Walter Berglund were the new pioneers of old St. Paul—the gentrifiers, the hands-on parents, the avant-garde of the Whole Foods generation. Patty was the ideal sort of neighbor, who could tell you where to recycle your batteries and how to get the local cops to actually do their job. She was an enviably perfect mother and the wife of Walter's dreams. Together with Walter—environmental lawyer, commuter cyclist, total family man—she...