"Upon first glance, Chip McGrath and Chip Gillespie were unlikely friends. McGrath was an Irish Catholic from working-class Boston, while the other Chip was a WASP, the son of a private school headmaster. McGrath was a draft dodger while Chip was a vet. McGrath and his family were summer people, while Chip and his wife called the little Massachusetts town with the tidal river their home. But somehow, over the course of one summer, then twenty,...