small fortune in a real estate transaction, Undine does not think twice about introducing him to Elmer Moffatt, her first husband, without of course informing Ralph that there had been a first marriage. Later, after she has divorced Ralph, her father tells her she must return a set of valuable pearls to Peter Van Degen (with whom she has had an affair) since everyone knows where they come from and she can never wear them in public. Undine very practically thinks that the pearls would be better disposed of by selling them to finance an escape from the censorious world of New York society. Later, when she wants to secure an annulment in order to make her acceptable as a French aristocrat's wife, she is quite willing to sell the custody of her son, leaving him with his father in exchange for a large sum of money. That this last transaction results in the suicide of Ralph Marvell is something that barely touches Undine's conscience. She feels "a vague sense of distress" when Ralph's name is mentioned even though his death has left her free to marry Raymond without getting an annulment. Nevertheless, she had not wanted Ralph to die—"at least not to die like that." Her marriage to Raymond de Chelles effectively comes to an end when she makes the practical suggestion that they sell the chateau at Saint Desert (the large, drafty dwelling which drains the family income and where she is bored out of her mind for ten months a year) and when she has the famous Chelles tapestries appraised. But after she divorces him, Raymond de Chelles actually follows through with selling the tapestries when he needs to raise money to cover lost income from the economic collapse of his brother's American father-in-law. In all these examples, Undine displays a hardheadedness and independence that enable her to come up with a practical solution.

The four men in Undine's life may be categorized by their style and appearance. Ralph Marvell and Raymond de Chelles are refined, elegant men from the best families. Undine at first hardly takes notice of Ralph, calling him "a little fellow," but as she comes to appreciate Ralph's position as an eligible bachelor from one of New York's oldest families, she also comes to admire his style of good looks, seeing him as a model of "finish and refinement" and thinking that these qualities "might be even more agreeable in a man" than in a woman. As a descendant of two of New York's oldest families, Ralph had been raised to lead a life of "more or less cultivated inaction."

Marriage to Undine is a disaster for him. Forced to leave his gentleman's profession of law and to give up his pursuit of letters, he enters a real estate firm with the sole aim of making money, something which he lacks any aptitude for. Raymond de Chelles reminds Undine of Ralph. She thinks of both men as "sweet," Raymond blending Ralph's "fastidiousness and refinement" with his own "delightful foreign vivacity." However, there is a big difference between the two men. Ralph never challenges Undine. Early in their marriage, he lets her have her way on their honeymoon when they leave Italy for Saint Moritz. Undine has found an agreeable social set at this resort, and Ralph does nothing to check her social progress. He does not approve of her cohorts, but he does not want to "mar her pleasure." This indulgence sets a pattern that remains consistent. Ralph never challenges Undine, even when he suspects she is having an affair with Peter Van Degen. He realizes that she has established the terms of their marriage and that she will always get her way in the end. In contrast, Raymond has no problem resisting Undine, even when he seems to be most ardently interested in her. Thus, Undine learns that her husband will not pay for her extravagant shopping sprees and that she is expected to live for ten months a year with her mother-in-law at the chateau in Saint Desert. When Raymond's sexual interest in her wanes, as had Ralph's, he is quite prepared to maintain an appearance of matrimonial harmony for the public, but he absents himself from any intimacy with Undine. She does her best to fight such a constricting marriage, but Undine soon learns that French custom goes against her desire for freedom.

The other two men in Undine's life are physically large and repulsive. Peter Van Degen bears a "grotesque saurian head, with eye-lids as thick as lips and lips as thick as ear-lobes." As he ages, he becomes broader and redder. She initially recognizes him because he looks like his picture that frequently appears in the society pages of the newspapers. His fashionable celebrity is enough to make him attractive to Undine. A hedonist, he is quite willing to spend lavish amounts of money on her while she is married to Ralph. Undine makes the mistake of thinking he will marry her after he has had an affair with her, but Van Degen callously rejects her, using her cold abandonment of her husband when he was desperately ill as a pretext for leaving her in the lurch after she obtains a divorce from Ralph.

Elmer Moffatt is described several times, perhaps most vividly when Ralph Marvell comes to see him about the status of his investment in the Apex Consolidation scheme. A large, red, balding man, his solid presence makes Ralph feel a "mounting pang of physical nausea." Undine recognizes Moffatt's physical grossness and crude manners, but she is overwhelmed by his energy, resourcefulness, and power. In the second half of the novel he becomes her primary advisor, making practical suggestions that enable her to extricate herself from her unhappy marriages to Ralph and Raymond. At the end of the novel, Undine has remarried Elmer. Appropriately these two people from Apex City establish their own version of a court in Paris. Elmer may lack the looks and manners to "fit into the picture" that Undine would create, but for the moment she seems almost content.