In the early parts of the novel Shaw goes to great lengths to make the point about "Jordache blood"– violent, bitter, resentful. One of the ways he does this is by meticulously describing the hate-filled marriage of the parents, Mary and Axel. The novel is told in the third person omniscient point of view but never wholly objectively, often through the lens of the consciousness of one of the five family members. When told through the POV of either Mary or Axel the view of humanity, and of the Jordache family, is relentlessly bleak and pessimistic.
The tripwire that sets all of the ensuing plot action in motion occurs when Gretchen Jordache begins an affair with the president of the company she works for, Teddy Boylan, a man much older than herself. Eventually her brothers Rudolph and Thomas also become involved with Boylan, in different ways, and it is his influence upon all three that first springs each of them into the world beyond the small upstate New York town where their parents scrape by with their bakery. Boylan constitutes their first true encounters with an adult beyond their parents.
Many people, mainly because of their familiarity with the miniseries rather than the actual source material, thought of the story as a very simplistic juxtaposition of the virtuous, goody two shoes brother (Rudolph) with the black sheep, ne'er-do-well younger sibling (Thomas, whom Shaw seeks to differentiate psychologically by means of a physical symbol– he is the only blond haired member of the family), but the novel is much more complex than this in its demonstrative understructure. For example, Rudolph is constantly developing positive relationships only with people who can help him - his father, Mr. Calderwood, Johnny Heath, Boylan. In starkcontrast to this both Gretchen and Thomas consistently entangle themselves with the kinds of people that modern self-help literature calls "drain people" or "toxic people". A couple of examples: Thomas' only friend in the world, Claude, gives him up immediately to the authorities the second his ownwell being is threatened, and when Axel Jordache learns of Tom's actions his only impulse is to get rid of him, to send him away to live with family in Ohio. Contrast this with Rudolph's friend, Johnny Heath, who becomes his lifelong friend, attorney, and business partner, and also with what Axel Jordache does when confronted by Rudolph's French teacher over a behavior miscue – he slaps the teacher in the face. We cannot imagine him defending either Gretchen or Thomas in this manner.
Boylan serves as the macguffin that drives the plot for all three of the Jordache siblings. For Gretchen he is an introduction to the world of men and relationships. He awakens in her the realization that she is the kind of woman who reduces men to cowering wimps but who cannot, perhaps somewhat paradoxically, put together a sound, completely fulfilling relationship. Her marriage to Willie Abbott collapses under the weight of his alcoholism and her marriage to Colin Burke ends in tragedy when Burke dies in a car accident. Similarly none of her numerous affairs bear any genuine emotional fruit.
It is because of Boylan that Thomas embarks on a savage act of vandalism (with his friend Claude, who eventually turns him in). When caught, the men of the town present Axel Jordache with a choice– send Thomas away or let him and the family face the consequences with the law. Jordache sends him away to live with his brother in Ohio, thus beginning a pattern that is repeated over and over and over in the novel: Thomas settles somewhere for a while, does OK for a time, then gets into troubleand has to flee.
Finally Boylan offers to pay for Rudolph to go to college. Although on one level Rudolph despises Boylan as a petty vindictive rich pervert of an old man, he sees another side of him as well - the financially independent man of the world who wants for nothing. Shaw uses Rudolph's even, balanced judgment of Boylan as a counterpoint to the wholly negative, wholly one-sided opinion of him both Gretchen and Thomas, in their own separate ways, cling to.