By Nightfall

Meet Peter and Rebecca Harris: mid-forties denizens of Manhattan’s SoHo, nearing the apogee of committed careers in the arts—he a dealer, she an editor. With a spacious loft, a college-age daughter in Boston and lively friends, they are admirable, enviable contemporary urbanites with every reason, it seems, to be happy. Then Rebecca’s much younger lookalike brother, Ethan (known in the family as M...