The young love motif
The main couple in this story gets married in the opening sequence, but that's not the only marriage in the book. Gibson marries Arabella French. Dorothy and Hugh Stanbury each have their romantic escapades. Nora has several suitors. Brooke Burgess has his flings as well.
In fact most of the characters are young single people desperately trying to navigate the landscape of their courtships. The various relationships each show what love is like to the characters. Some are passionate, some are considered, but all the young people in the book are in the business of falling in love.
The cheating and dishonesty motif
Just because this book focuses on young love and marriage, that doesn't mean that it's a fluffy, light-hearted tale. No, in fact, the young couple at the center of the story, Louis and Emily, struggle almost immediately. After the birth of their boy, their trust and commitment is tested by Emily's wandering eye.
Louis seems to realize almost immediately (as the title suggests) that, although Emily is probably not technically cheating on him (as the ending of the novel suggests) that her relationship to the Colonel is romantic in nature. This leads to a series of disappointing fights where they each find out aspects of the other person that they don't like, and they begin drifting apart. The motif occurs in other side stories too as various couples argue, split, and cheat on each other.
The spinster
In the novel, there is an old, single spinster who involves herself in young people's drama. Her function seems to be that she serves as a kind of guardian over the problems of young love. She is extremely conservative and fundamentalist in her political beliefs, which is an indication that she represents something old-fashioned. In this case, she is like the pushy grandma who always seems to be match-making, almost as a hobby.
The spoiled wife
Emily doesn't really handle disappointment that well in the novel, and she almost immediately plays the victim when her husband points at her strange, seemingly sexual relationship with the Colonel. Remember that Emily's father was the governor of an island, and she was raised in lavish luxury, alongside her sisters. In other words, maybe Emily is not oriented to sacrifice in her marriage, not because she's evil or something, but just because she was spoiled, and the experience of disappointment is traumatic to her for that reason.
The insecure husband
Without much life experience to anchor Louis's character, he develops a serious case of insecurity. When he learns that his wife has been entertaining herself on dates with someone else, he doesn't see that as an opportunity to re-evaluate their relationship, and he doesn't pause to consider that he might be neglecting her or something. Instead, he instantly sees Emily's wandering eye as a reflection of him.
For Louis, everything is a dilemma of self-esteem, because he lacks it. When Emily seems to be rejecting him in their marriage, he doesn't see that as a problem to be fixed; he sees it as an opportunity for negative emotion. Then things become even more unstable and disappointing for both parties.
