Adam Trask has unsuccessfully sought a peaceful relationship with his half-brother, Charles, because their father, Cyrus, has always favored Adam with obviously preferential treatment. Afraid of Charles's violence, Adam is forced into military life, which he hates, just to get away from Charles. He falls hopelessly in love with Cathy, whose evil character he cannot discern. He cannot understand what she wants and is left in shock when she shoots him and leaves after she gives birth to their twin sons, abandoning him to raise the boys with his housekeeper and cook, Lee. As a father, he ends up favoring his son Aron over the brooding, more loving, and complicated Cal, whom he treats coolly and often thoughtlessly. However, as Adam is dying, he blesses Cal.
Patriarch of the Hamilton family, Samuel Hamilton is the narrator's grandfather. He and his wife have a large family and live simply on dry land that cannot be farmed. Samuel develops a gift for finding water on other properties, but inadvertently keeps his family in straitened financial circumstances because he neglects to ask for payment due him. He is a generous, well-respected man who reads widely and teaches his children—all of whom he delivered himself with guidance from a medical book—to love learning. He serves as a spiritual mentor and friend to Adam and Lee.
Charles Trask grows up both loving and hating his brother, Adam, all-encompassing sentiments that dictate his behavior throughout his life. He wants Adam nearby but flies into rages and beats him when Adam succeeds at anything to a greater degree than Charles does. Charles's rage is motivated by jealousy of their father's preference for Adam. A hardworking farmer, Charles definitely has an evil side, for he willingly sleeps with Adam's new wife, who is even more manipulative and evil than Charles. He spends the rest of his life alone, amassing wealth and loving no one.
Cathy Ames begins her career as a sexual predator of sorts by falsely accusing boys of attacking her. Later she causes a young teacher to fall in love with her and subsequently kill himself. She kills her parents to get their money and becomes a prostitute, who steals from her boss. She cons Adam into thinking she loves him so he will take care of her while she heals from a severe beating. After she and Adam marry and she gives birth to twin boys, whom she unsuccessfully tried to abort, she shoots her husband, leaving him and returning to prostitution. After murdering the madam, Cathy inherits the brothel, running it as the most depraved establishment in Salinas. She keeps her prostitutes addicted to drugs so they will comply with sadistic and sadomasochistic acts. Cathy never questions her motives or actions, remaining evil throughout the novel. She ages badly, in constant pain from arthritis, and loses her innocent beauty but not her depravity.
Cal (Caleb) Trask, one of Adam and Cathy's twin boys, spends his childhood alternately being jealous of the way others tend to see his brother, Aron, as innocent and angelic, and trying to protect Aron, whom he loves. To gain his father's love, Cal goes into business with Will Hamilton and makes enough money to help his father recoup financial losses, but his father rejects the money, believing it to have come from underpaying farmers. When Cal sees Kate and the horrible things she does, he realizes he can take his life into his own hands and change the direction his character is taking.
Aron Trask, one of Adam and Cathy's twin sons, is a fair-haired, naive young man who wants to be mothered so badly he turns his girlfriend into an idealized mother figure. Yet, he alienates his girlfriend by ignoring her wishes, obsessing over religion, and insisting on purity. When Cal, his worldlier brother, reveals the identity of their mother—an act of revenge for being more loved by their father—Aron joins the military and is killed soon after.
Adam Trask's cook and housekeeper, Lee is an intelligent, wise, college-educated man who pretends to speak broken English to people who expect it of him but speaks fluent English with Samuel Hamilton, whom he befriends, and later with Adam. Adam's twin boys love and revere Lee, who is their caregiver and the Trasks' spiritual guide. Lee prefers working in the Trask household to working outside of it because he feels safe and loved where he is. Lee has the ability to see the larger world and humanity's place in it. He is also able to point out and encourage the strength people have to change their destinies. He takes care of and guides Adam through every success and failure.