The son
Over the course of this novel, Undine marries like the woman at the well. By the end of the book, she has had four spouses at least—there might be more. In all those marriages though, she only ever had one son. The book zooms right in on that situation in the first act to expose the flaw in Undine's character. One could say that she is entitled to live her life the way she wants—of course she has an extremely negative effect on her spouses, but that is the gamble of marrying someone. However, with a child in the picture, Undine's selfish and entitled ways are plainly irresponsible and unethical.
Ralph's suicide
All the husbands are basically symbolized in Ralph, because we meet Undine in relationship to Ralph. In her world, he is one person in a long serial list of spouses. To her, marriage is a game, a tool for her to be able to quickly attain a life that typically people have to work to attain. She does not have empathy for others because of her desire for money, so she does not know that she is destroying the lives of people who are as important as she is. Ralph's suicide portrays the ultimate pain of rejection and confusion that Undine's behavior causes.
Undine's archetype
Undine has an archetypal relationship with money, because she is destroying the lives of men to attain her desires. There is a name for this in literature: femme fatale. She is a deathly woman who brings men into turmoil so unbearable that men like Ralph cannot bear it. She is the femme fatale for the usual reason—an obsession with attaining her desires, especially money. She is like the money-hungry woman who lies with the beast in Revelation. She is like Helen of Troy in certain Greek stories.
The secret ex-husband
Ralph's difficult circumstance brings him to his knees. In the meantime, Undine has been accruing new spouses. This means that she might have been doing that before the novel begins, which we know to be the case because of what Moffat says to her late in the novel, before Ralph's suicide. Moffat symbolizes Undine's past, her relationship to the spare and flat lands of her Midwest upbringing, her relationship to money (Moffat gives her money). In a way, he symbolizes an accepting attitude.
The antithetical argument for marriage
In Undine's character, the reader has a fairly thorough idea of what not to do in a marriage. By inverting her flaws, an argument about marriage can be seen. Basically, the idea would be empathy. Marriages need to be rooted in mutual empathy. Undine shows the opposite, because she does not even realize that the other people around her, even her own husbands—she does not really understand the value of their existence. She really only sees life as it relates to her desires. This ethical reading shows that marriage is easily exploited, and of course Undine's relationship to money is a symbol; in truth, the ethical reading would apply to any marriage where someone is trying to fulfill their desires by using the other person.
