Although he is at heart a positive, sunny character, Samuel Hamilton sinks into a deep depression as he returns home from dinner at the Trask ranch. As his faithful horse pulls his cart home on a star-studded evening, Samuel begins feeling unwell, and recalls a time during his youth in Ireland when he went with his father to town, where they saw a handsome young man being excoriated by a crowd. Samuel shudders as he recalls the man's inhuman eyes - the same merciless eyes that he has just encountered in the visage of Cathy Trask: "The eyes of Cathy had no message, no communication of any kind. There was nothing recognizable behind them. They were not human eyes." The man Samuel saw as a child was executed in front of him because he was thought to be evil incarnate, a devil in human form. Try as he might, Samuel cannot get the horrible image out of his mind. He remembers how the man was thought to be lacking an essential human component, and realizes that Cathy Trask is similarly without this crucial element. When he returns home he is glad to see his practical wife, Liza, and informs her that - despite her advice to the contrary - he has agreed to help Adam rebuild his ranch. Some time later, Samuel, who delivered his own children, is called upon to help Cathy when she goes into early labor. On their way to the ranch house, Samuel and his Chinese-American friend Lee, who is the Trasks' servant, share their similarly negative feelings about Cathy. At the house, they find Adam fretting, and ask the nervous father-to-be to leave. Samuel finds Cathy in a darkened room and opens the blind to let in light, making her diabolically angry. She hates Samuel, and bites him when he attempts to comfort her during her labor. After giving birth to twin boys, Cathy refuses to see them or nurse them. Samuel is shocked by Cathy's unnatural behavior and sends for Liza to help. Cathy informs Adam of her plans to leave within a week after giving birth. He dismisses her words as ravings brought on by the trauma of childbirth, but later she proves him wrong, shooting him in the arm when he attempts to stop her. Horace Quinn, the local deputy, refuses to believe that the shooting was an accident - especially when he learns that Cathy has left the ranch. He informs the Salinas sheriff, who has heard that Cathy is working in Faye's brothel, about the events. They decide to keep Cathy's whereabouts secret from Adam to protect the children from the knowledge that their mother is a prostitute. Samuel and Adam become close friends while Adam recovers. The older man tells Adam that he too has suffered, and assures him that by going through the motions of living he will heal in time. Adam has no idea that his wife is still in Salinas, residing in a house of prostitution.
The houses of prostitution in the Salinas Valley attract a variety of clientele by specializing in different sexual fantasies. Faye's, the brothel where Cathy (now "Kate") winds up, provides homey comfort in addition to sexual release, but does not condone any extreme sexual practices. Faye is well-liked by the authorities because she keeps an eye out for the criminal element amongst her clients and donates money to the local charities. Kate endears herself to Faye, and quickly becomes indispensable to the older woman. She organizes the house, ingratiates herself to the other girls, improves the menu and working conditions, and saves Faye a great deal of money. The sheriff, whom Kate likes for his direct and truthful manner, pays a visit to Kate after hearing of Adam's shooting, but cannot do much because Adam has not pressed charges. The sheriff warns Kate to keep a low profile, and to stay away from her sons - and his own son, for that matter. In addition, he orders her to dye her hair black so that she will not be recognized.
Eventually, Kate becomes so indispensable to Faye that she begins to think of her as her own daughter. At a private party, she informs Kate that she wants her to stop working as a prostitute: "You could take care of things for me and not go upstairs." She informs Kate that she wishes to be called "mother", and tells her that she is the sole beneficiary in her will, ordering Kate to drink champagne to celebrate. Kate, who loses control when she drinks, becomes hostile, calls Faye a fat worm, and lets slip that she has, unbeknownst to Faye, been making a lot of extra money by engaging in lucrative sadomasochistic sexual adventures with clients who ask for such services. Gone is the good daughter routine, and the vile being that lies underneath the facade is now apparent to all. Faye is horrified by the revelation. However, after Kate sobers up, she drugs Faye with an opiate and convinces her upon waking that the happenings of the night before were all part of a bad dream. The distraught Faye, who wants more than anything to be cared for and loved, believes Kate. At this point, Kate takes control of the brothel and begins to poison Faye. She feigns illness herself so that Doctor Wilde will provide her with the medication she needs to kill Faye, thus making it appear as though her death is the result of natural causes. When Faye dies, Kate buries the bottles of poisonous medication in the backyard. To observers, she appears to be a distraught daughter, abject with grief. She loses weight and takes to her bed, and her devotion goes unquestioned. The entire time in the brothel, Kate never once thinks of Adam Trask or her twin boys.
In the wake of Cathy's departure, Adam sinks deeper and deeper into lethargy and despair. After more than a year has gone by, Lee complains to his friend Samuel Hamilton that Adam has not yet even named his twin sons. Lee has, in effect, become the boys' mother and father - they have even begun to say Chinese words. Samuel Hamilton comes immediately, and finds Adam deep in depression, seemingly unable (or, Samuel thinks, unwilling) to help himself: "It seemed to Samuel that Adam might be pleasuring himself with sadness." However, after a few failed attempts at talking to Adam, Samuel hits his friend to jolt him out of his despair. Lee, by now speaking proper English, joins Samuel and Adam for a drink while the babies sleep in the warm dust. The men begin an intellectual discussion about the story of Cain and Abel, and analyze the continuing human cycle of rejection, anger, revenge, and guilt. Although Samuel suggests the names Cain and Abel for the boys, they decide to call the children Caleb (after the man who made it to the Promised Land) and Aaron, who failed in the attempt. Over time, the names morph into Cal and Aron.
Steinbeck continues to juxtapose good characters with evil characters in an effort illustrate one of the novel's primary themes: the battle between good and evil. The upright, honest Samuel, who symbolizes God the Father, becomes severely ill after the satanic Cathy bites him on the hand when he attempts to help her during labor. Here, good clashes directly with evil, and the poisonous Cathy's evil is so powerful that it incapacitates - indeed, almost kills - Samuel Hamilton, who is goodness personified. Samuel must turn to his benevolent wife, Liza, to give him strength and restore him. As they are both mother-figures, there is an inevitable contrast between Liza and Cathy: Liza is a self-sacrificing, adoring mother, while Cathy refuses to look upon her children's faces or care for them, and even abandons them as soon as she is physically capable of doing so. Not for a single instant does she consider her children's well-being. Liza, the loving mother of nine, arrives to save the day: she, it seems, is the only one capable of curing Samuel of the damage done to him by the evil Cathy. Along with Lee, she helps care for the newborn twins. Liza's relentless cleaning of Cathy's newly renovated home signifies that the Trask house is dirty and diseased.
Steinbeck has received a great deal of negative criticism for this dramatic juxtaposition of good and evil characters. His characters, many scholars maintain, are simply not real enough to be convincing. However, it could be argued this is exactly what Steinbeck set out to accomplish, because he wanted to reach as many people as possible and have his stories impact them in the manner of biblical parables. In East of Eden, he offers a simplistic personification of good versus evil (Samuel and Liza Hamilton versus Cathy Trask). Similarly, Quinn and the sheriff are cast as good characters, almost guardian angels, who protect the Trask babies from contamination by their evil mother. In addition, the sheriff is cast as a good father (in contrast to the weak, incapacitated Adam) when he warns Kate to stay away from the twins and from his own son.
Faye is an interesting character: although she is a brothel owner, there is nothing inherently evil about her. In fact, she gives more money to the local charities than most business owners. She also views her girls in an almost motherly fashion, and treats her customers well. As the novel progresses, it becomes clear that Faye is intended to be juxtaposed with Kate, who eventually takes over the brothel and runs it in a particularly vile manner.
The juxtaposition of good and evil characters continues with Samuel Hamilton and Adam Trask: Samuel is the epitome of the good father figure, while Adam pays virtually no attention to his children. Samuel fathers nine children, all of whom turn out to be good people. He cares deeply for each, and respects their unique talents and failings. Adam, on the other hand, fails to give his children names even more than a year after their birth. This might suggest that Adam on some level enjoyed his treatment at the hands of the sadistic Cathy. After all, Adam's ongoing despondence over his clearly evil wife leads the reader to wonder if, in the end, he is any better a person than Cathy. Adam grew up under the influence of a particularly cruel father, but seems unable to treat his children any better than he was treated himself. However, Steinbeck does suggest that people are different in different phases of their lives, and that they have the ability to change. This idea is expanded upon later in the novel through the central concept of timshel. Since familial relationships play a particularly important role in this novel, it is especially pertinent to note that Steinbeck's idea of forgiveness holds that individuals have the power to alter family dynamics. At this point, the reader should recall the rejection of Adam's brother Charles by their father Cyrus, which echoed God's rejection of Cain in favor of Abel. Charles' subsequent anger toward Adam nearly resulted in Adam's death. As the novel unfolds, will Adam become a better father, or will the cycle established by Cain and Abel be repeated in the Trask family once more, causing Adam to repeat his father's mistakes?
The biblical story of Cain and Abel, which is thematically central to the novel, is brought into sharper focus in this section. Samuel even suggests naming the children after Cain and Abel, but Adam rejects this morbid idea. Samuel, Adam, and Lee discuss the story at great length, even going so far as to read the Bible. They mull over each word, and wonder aloud why God chose Abel's gift of a lamb over Cain's gift of grain, but cannot find an answer. They also examine God's decision to cast out Cain and force him to wander the earth, discussing what, exactly, God promised Cain. Did God give Cain any hope for the future, or was he forever condemned? If no hope was offered, then are the descendants of mankind doomed to repeat the sins of their fathers over and over again, with redemption forever lying out of reach? During the philosophical debate, Adam argues that repeating the negative cycle of anger, revenge, and subsequent guilt is not preordained. After all, he remarks, he never even considered killing his own brother, Charles. However, he becomes much quieter after recalling the time when his brother almost killed him in a jealous rage.