As Cal becomes older his restlessness increases, and he begins wandering the streets of Salinas at night, wondering why everyone has lied to him about his mother. When a drunk named Rabbit Holman (who doesn't know Cal's identity) invites him to Kate's brothel after informing him that the owner is Adam Trask's wife, who shot her husband in the arm, Cal is confronted with the truth about his mother. Young Cal is stunned - to put it mildly - and runs to Lee for an explanation. Cal is extremely worried that he has inherited his mother's evil nature: "I hate her because...I've got her in me." Lee soothes the confused teen by assuring him that he can choose goodness over evil at any time. Cal realizes how much he loves his father, and his desire for Adam to return that love increases. In marked contrast to Cal, Aron moves ever deeper into religion. He joins the Episcopal Church and tells Abra (who is none to happy about these developments) that he plans on living a life of celibacy. Cal, whom Aron has labeled a sinner, thinks about telling Aron about his mother to get him off his high horse, but refrains because he believes that Aron is too psychologically vulnerable to endure the pain of this revelation. While his brother prays, Cal continues his nighttime wanderings. One night, he is arrested during a police raid, and Adam comes to bail him out. For the first time, Adam tells his mortified son about his sojourns in jail as a young man. Cal is amazed to learn that his father spent time on a chain gang. Cal then tells Adam what he knows about Kate, and both agree to continue to keep the truth from Aron.
However, Cal cannot get his mother out of his mind, and begins to stalk her "to learn all he could about her." He waits outside the brothel and follows her on her errands, and even arranges his classes to accommodate her schedule. One day, Kate notices that someone is following her and confronts the stranger, only to discover that it is her son, Cal. Inside the whorehouse, she takes him into her "gray room", explaining that she stays in the dark room because the light hurts her eyes. Cal notices that her hands are gnarled from severe arthritis. After inquiring about Aron, Kate begins to mock Cal's father, but Cal refuses to listen to her slander. She tells Cal that she believes that he and she are very much alike: "you're my kind. Maybe you're the same." The idea horrifies Cal until he recalls Lee's contention that all humans have free choice. He does not have to be like his mother. He tells her that he was once afraid that he was indeed like her, but that he is no longer worried. Call then tells her that he believes that she doesn't live in the gray room because of her eyes, but because she is afraid. At this point, Kate becomes angry. Unable to stand being called weak, she tells him to leave. "I'm going," he says, "but I'm glad you're afraid." After he leaves, Kate looks down at the vial of morphine that hangs around her neck. Cal hit a bulls-eye when he told her that she lived in fear. At this point, Steinbeck reiterates how Kate has been living since learning about Charles Trask's inheritance. Shortly after she took the money, she began to be troubled by arthritis pains. She was also disturbed by a visit from Ethel, a prostitute who used to work for Faye. Ethyl told Kate that she had the empty bottles of poison that she had buried after killing Faye, and attempted to blackmail her for $100 a month. In a panic, Kate has Ethyl arrested and ordered to leave town, but she becomes increasingly paranoid that Ethyl might tell someone else about Faye's unnatural demise. Worried that her actions might come back to haunt her, Kate decides to save even more money so that she can move to New York. She retreats into her gray room and rarely leaves the building. When she realizes that a stranger - Cal - is following her, she becomes even more distraught.
As World War I approaches, Cal suggests that he and Aron leave school and return to the family ranch to earn money. Cal wants to help his father, but Aron wants to leave Salinas and go away to college because he still feels humiliated by his father's failed business venture. However, Aron is afraid that his father might not have the money for the tuition at Stanford, the school he wishes to attend. The ever-practical Cal convinces Aron to take extra classes and graduate from high school a year early so that he can go to college sooner. Lee offers Cal his life savings of $5,000 to help finance a business venture. Although he is still a teenager, Cal demonstrates a strong sense of business acumen by going to see Will Hamilton. He forms a partnership with the wealthy son of Samuel Hamilton to market beans during the upcoming war. Their plan is to guarantee the Salinas farmers five cents per pound of beans (instead of the 3.5 cents they presently receive), and then sell the beans overseas at a tremendous profit after the war breaks out. However, World War I doesn't seem real to the town of Salinas, and it isn't "until the dreadful telegrams began to sneak sorrowfully in" that the town comes to realize the real impact of war. Steinbeck underscores the incongruity of being 6,000 miles from the noise of war, yet feeling the agony of losing loved ones nonetheless. No mention is made here of the effect of the war on the Trask family, which has two draft-age sons.
Adam feels inordinately proud of Aron's academic successes, especially when he learns that he is secretly working hard to finish high school a year early. He tells Lee, "I'm proud of him. Terribly proud," and says how much he wishes that Cal could show the same academic inclinations. Maybe, he says wistfully, Cal is also secretly working on something wonderful. Adam clearly favors Aron over his other son, to Cal's great consternation. Aron spends much of his time studying with Mr. Rolf, an Episcopal minister who comes to have great influence over him. When Aron does indeed pass his college entrance examinations a year early, he fails to tell his father, who has a gold watch waiting for the graduation announcement. All Aron can think about is getting away from this "dirty town": "I want to go away," he tells Lee, who responds that "things are neither so good nor so bad as they seem to you now." Lee advises him that if he pretends that everything is fine and goes through the motions of living well, things just might become better in time. Then Lee tells Aron that his father has left a graduation gift for him under his pillow.
After Adam goes off to Stanford, he finds - to his great consternation - that college is nothing like he expected. Desperately homesick, he writes letters to Abra full of love and promises, but has no interactions with the other students. In his absence, Abra visits more and more with the Trasks, and in short time becomes almost a member of the family. She becomes particularly close to Lee, and tells him all about her family. When she asks Lee about Aron and Cal's mother, Lee tells her the truth. Abra also voices her concern about Aron's false impression of her. She insists that she is just a normal human being with both good and bad characteristics, and worries that she will never be able to live up to Aron's expectations. She feels that he thinks of her as far too pure, and doesn't see who she really is.
While Aron is living in a religious fantasy, Cal finds himself solidly enmeshed in the real adult world. He pays back Lee's original $5,000 loan and plans to tell his father of his successful business venture on Thanksgiving, when he plans to give Adam a gift of $15,000 to restore the family's financial losses. He talks with Abra, who confides in him that she is not as perfect as his brother thinks she is. Cal, however, doesn't take her seriously.
Simultaneously, things are heating up on the other side of town, at Kate's brothel. Kate's bodyguard, the escaped San Quentin convict Joe Valery (who works at the whorehouse as a pimp) is sent by Kate to track down Ethyl. Her paranoia has continued to escalate, and she can no longer contain her anxiety about the possibility that Ethyl might be speaking to others about the circumstances of Faye's death. The ruthless and savage Joe has taken over more and more of the responsibilities at the brothel, as Kate's arthritic hands keep her from being too active. He realizes that Kate is losing her mind, and sees this as an opportunity to get more money out of her. Kate, however, mistakenly believes that she can control him, and offers him $500 to find and dispose of Ethyl. After wandering around the nearby towns of Monterey, Watsonville, and Santa Cruz, Joe learns that Ethyl has drowned, but tells Kate that she is alive and planning to return to Salinas. Kate has since seen her angelic-looking son Aron from a distance, and has been feeling much better, having even begun dreaming of moving to New York, establishing herself as a respectable woman, and having her son come to visit. The news about Ethyl, however, throws her even deeper into her paranoia, and she locks herself in her gray room. Joe sees how much his news disturbs Kate, and erroneously comes to believe that he is gaining power over her.
Ever since their birth, it has appeared as though the devout, angelic-looking Aron is destined to do good, while the darker Cal is fated to be evil. The natural assumption is that the Cain and Abel story will play out in this generation as well, with Cal murdering - or at least harming - his brother in a jealous rage. However, this black-and-white proposition takes on shades of gray as the twins approach adulthood. Indeed, Aron seems to be out of touch with reality, and as he sinks deeper and deeper into religious fanaticism, his innate selfishness reveals itself. He scorns his father and continues to feel great shame over the family's financial losses even after he reaches an age when he should be able to understand the realities of the business world. Although he is angry with his father, he nevertheless runs away to school and allows Adam to support him. He idealizes Abra, but never takes the time to get to know her as a human being. He puts her on an impossibly high pedestal, yet fails to consider her desires when he announces his plans to live a life of celibacy.
Unlike Aron, Cal seems to be evolving into a responsible, caring adult. He supports his brother throughout high school, and continues to help pay for his college tuition. He saves money so his father can regain his financial standing (even though it is worth noting that he earns the money by taking advantage of the need for food during wartime). Although he is attracted to Abra, Cal respects the fact that she is his brother's girlfriend. He also treats Lee with great consideration and kindness. Cal spends his nights wandering the town, gambling, and seeing prostitutes, but this behavior causes him great concern. Even though Cal is cast in the dark role of the biblical Cain, he struggles to become a better, more moral person. He loves his family, and displays a strong sense of intuition in recognizing the deadening fear that lies behind Cathy's brusque behavior. Indeed, he has an aptitude for understanding the intricacies of evil and goodness - a trait that Abra later comes to admire. Eventually, she falls in love with Cal, preferring his realistic view of her to Aron's idealization. Here, Steinbeck returns to the concept of timshel, or free will: Aron remains a deluded, ill-tempered child, while Cal struggles to become a better man.
In this section, Steinbeck also juxtaposes Aron with Adam. Father and son are remarkably alike, and are an apt demonstration of how family history is oftentimes repeated. At the beginning of the novel, it becomes clear that Adam hates his father, Cyrus. Similarly, near the end of the novel we learn that Aron hates his father, Adam. Even so, both fathers love the son that does not return their affections more than the son that adores them. Cyrus loved his older son, Adam, more that he did his younger son, Charles, as was evidenced by his preference of Aron's gift of a mongrel puppy over Charles' gift of an expensive knife. Charles, he believed, had a dark nature, and Cyrus kept him at a distance instead of attempting to find out how he could help his unhappy son. Similarly, Adam adores Aron, while Aron despises his father for no good reason. Aron is in fact cruel to his father, and runs away to school simply to get away from him. Adam turns a blind eye to this treatment, as he once did to his wife, Cathy. Indeed, Adam's feelings for Cathy seem to be the root of this preference. In time, Cal comes to realize that Adam favors Aron because of his physical resemblance to their mother. Adam is also blind to the affections of Cal, the son who loves him more than anyone else on earth, and fails to recognize all that his son is doing to help him. This tension continues to surface in the last part of the novel; once more, family history repeats itself when Cal gives Adam the $15,000 he earned to restore his father's fortune.
Although Steinbeck primarily focuses on his male characters, he draws a comparison between two important female characters: Cathy and Abra. Early on, Adam viewed Cathy as innocent and pure, and his son Aron views Abra in a similar light. He places her on such a high pedestal that she has nowhere to go but down. Cathy and Abra must therefore be viewed through the same lens. If Aron and Adam are so similar, can Abra and Cathy really be so different? In other words, is it possible that Abra might turn away from her inherent goodness and embrace her dark side? Abra fears this possibility more than anything, even asking Lee about her evil impulses. She feels that Aron holds her in far too high regard, and tells Cal that she is not as pure as she seems. The discovery that Abra's father is a thief only escalates her worries in this regard. However, an analysis of the two women as children reveals their inherent differences: Cathy never once did a good thing for anyone, while Abra was a sweet child who demonstrated an early maternal tenderness, comforting Aron when he needed her most. Abra, like Cal, recognizes that all humans have impulses towards evil, but that each individual has the ability to choose to live a good, moral life.