As editor-in-chief of New York’s leading fashion magazine, Fiona Monaghan was utterly content with her life, jetting back and forth between her stylish Manhattan and Europe—until the sweltering June day John Anderson strolled into her office. A widower with two daughters, John was as conservative as Fiona was freewheeling, both amused and appalled by her world of high-strung designers, anorexic models, Fendi-stuffed closets, and Sir Winston, her...