When the novel opens, Dick Diver is presented as a "golden boy," with charisma and looks that reach godlike proportions. People are drawn to him like a magnet, and those in his inner circle depend on him to provide both fun and stability. Yet from the beginning, Dick's flaws are noticeable. He is a narcissist who craves to be the center of attention and admiration. Dick chooses to marry Nicole because he likes for her to need him in every way—for love, for psychological care, and for a strange mixture of fatherly protection and sexual attention, which reflects her incestuous experience with her father. Similarly, Dick falls in love with Rosemary because he wants her to need him. And when his relationships with Nicole and Rosemary begin fading, he turns his attention to his children, desiring their adoration. Dick's decline is tragic as he goes from being a talented, sometimes sweet and caring, and charismatic man to an angry, weak, unsteady mess. Yet his fate has always been in his own hands, and he makes the choices leading to his downfall. He doesn't have the discipline to attend to his work, to avoid the lures of a wealthy and decadent lifestyle, or to deny himself pleasure from being adored and then responding immorally. The frustration many readers feel at the end of the novel, when Dick seems to simply evaporate into an insignificant life, is dismay at having watched a life of promise thrown away.
Nicole makes a radical transformation in the course of the novel as she gains strength and a level of mental stability. Fitzgerald makes it abundantly clear just how ill Nicole is, showing in the first-person sections her insane thoughts and split personality, revealing how many breakdowns she has, and hinting through other characters' reactions just how bizarre her behavior can be. Yet when Dick begins to weaken himself and fall into unhealthy and unstable patterns of behavior, Nicole gains strength. Nicole saps Dick's strength and makes it her own, and then has no use for him. She is free to move on and able to have a sexual relationship with Tommy Barban, who is now much stronger than Dick and able to keep up with her wealthy, privileged lifestyle. Once the tragic character, at the end of the novel, Nicole is the survivor.
Rosemary is not much more than an adored, pampered child as the novel begins. Her mother has plotted her life for her, and Rosemary has gone along with it. Rosemary is a successful actress; the underlying question about her character is, does she act her way through life as well? Her public image must match her image in her hit film Daddy's Girl, but that doesn't seem to bother her. She is happy to live however people tell her to live. Rosemary doesn't have much depth as a character, and any real development is hard to trace. By the novel's end she is a bit more sophisticated as a gorgeous, sexually desirable female, but she seems likely to continue following others' ideas about how to live, by marrying her costar and fulfilling her fans' dreams. According to the New York Times, the character was based on a beautiful 1920s ingenue named Lois Moran, whose first big film was Stella Dallas.