Well-mannered and well-educated, 27-year-old Frederick Winterbourne has lived in Europe for so long that he has forgotten the nature of American culture and Americans themselves. Although he is devoted to an older "foreign lady" in Geneva, he is captivated by Daisy Miller's beauty and flirtatious manner. Daisy is Winterbourne's complete opposite—she lives life to the fullest, making friends wherever she goes and refusing to let others' opinion of her influence her actions. Winterbourne is bound more closely by restrictive European social customs. What attracts Winterbourne to Daisy is what also scares him. He worries a great deal about how Daisy's unconventional behavior may reflect upon him. Could a woman so free with her attentions and her reputation truly be "a nice girl"? Winterbourne, who is used to the strict social customs of Geneva, ultimately determines Daisy couldn't possibly be as innocent as she claims, and he decides to cut her out of his life completely. He isn't worried about her reputation, but his own. After Giovanelli insists that Daisy was "the most innocent" woman he knew, Winterbourne feels bad for a time that he misjudged her, but ultimately returns to his old life in Geneva, an apparently unchanged man.
Daisy Miller, born Annie P. Miller, attracts attention wherever she goes, and it isn't always positive. There is something about her that rankles those who have lived in Europe for a long time. It could be her family's relatively new wealth, her overly familiar relationships with men, or her general disregard for European custom. Though many have tried to set her straight about what is and isn't acceptable, Daisy refuses to listen. She does what she wants when she wants, and most of the time she wants to be the center of attention. James himself insisted that Daisy was merely ignorant of the customs ingrained in European high society and unfairly punished for it, but her motivations in the novella remain debatable.