Cathy believes Charles to be a great deal like her and fears him because of it. She is relieved to find that Adam, on the other hand, is easy to manipulate. When Adam suddenly asks Cathy to marry him, she considers the safe harbor that marriage would provide her and accepts his proposal, although she asks Adam not to tell Charles. Charles grows more suspicious of Cathy when a neighbor discovers a suitcase full of money and clothing near the site of her beating. But as soon as Charles leaves the house, Adam takes Cathy into town and marries her.
Charles becomes furious when he discovers that Adam and Cathy are married. Cathy is dismayed to learn that Adam intends to move her to California. That night, Cathy tells Adam that she is still too badly injured to sleep with him. She drugs Adam with a sleeping medication and then goes to Charles, who takes her into his bed.
When Cyrus Trask dies, he leaves a suspicious inheritance that threatens to taint his family for generations afterward—a symbolic parallel to the biblical idea of original sin. According to the Christian tradition, Adam and Eve are created as sinless beings and sent to live in the earthly paradise of Eden. However, they fall into sin after Satan, in the form of a serpent, tempts them into eating the fruit from the tree of knowledge of good and evil, which God has forbidden them to eat. In punishment, God curses Eve to suffer painful childbirth and to submit to her husband’s authority; he curses Adam to toil and work the ground for food. Then, God banishes Adam and Eve from Eden. Adam and Eve pass this original sin on to all their descendants, who are born as already sinful beings. In East of Eden, Cyrus’s dishonestly won fortune, which he either steals or gains from a career built on lies about his supposed Civil War experience, is a symbol for this original sin. The result of Cyrus’s sin—the inheritance of $100,000—literally is passed on to his sons.
After Cyrus’s death, Adam and Charles live together on the farm as equals, but the vast differences in their characters and attitudes drive them apart. Charles is cynical and pragmatic, obsessed with work, money, and gain. Adam, meanwhile, is idealistic, uninterested in the financial aspects of life, and longs to travel and see the world. Furthermore, we see that Charles still resents the incident of Cyrus’s birthday gifts, as he uses his memory of the event as the basis for the password that Adam must use to collect money from the telegraph official. Charles and Adam also are deeply divided in their attitudes toward their inheritance from Cyrus: Charles believes that Cyrus stole his fortune, but Adam disagrees, refusing to believe the possibility that their father could ever be dishonest. The narrator explains this disagreement as a result of the fact that Charles loved Cyrus, whereas Adam did not; he says that people are always suspicious and skeptical about those whom they love.
Steinbeck counters this argument about love, however, with his portrayal of Adam’s blind, naïve devotion to the treacherous Cathy Ames. Cathy appears in this section as the novel’s definitive embodiment of evil. Driven by self-hatred, desperation, and a love of pain, she destroys lives without remorse. She uses sex as a weapon, causing her lust-crazed teacher to commit suicide; in fact, later in the novel, she reveals that his depression and desperation over her rejection of him kept her up at night laughing. Cathy murders her parents and becomes a prostitute—apparently out of an insatiable need to be evil—and seems pleased with her decision, as though life as Mr. Edwards’s whore is an improvement over life with her loving parents. As an embodiment of pure evil, Cathy is a perverse caricature of the biblical Eve, who first introduced sin into the world by eating the forbidden fruit. Similarly, Cathy—married, like Eve, to Adam—brings evil into Adam’s world and later gives birth to Cal and Aron, two more characters who directly mirror the biblical Cain and Abel.
Charles, in contrast to Adam, is suspicious of Cathy from the start, perhaps because at some level Charles and Cathy seem to be cut from the same cloth. Thus far, Charles is the only character able to out-manipulate Cathy, and he does so to the point that she becomes frightened of him. The fact that Cathy gives herself sexually to Charles on the night of her marriage to Adam highlights her strange connection to Charles as well as the strange connection between the brothers. By the same token, the fact that Charles allows his brother’s wife into his bed shows the extent of his cynicism, hypocrisy, and immorality. Charles would risk killing Cathy to get her out of his house, as keeping a woman could damage his reputation; at the same time, however, when Charles learns that Adam has been drugged and will therefore not discover Charles’s treacherous adultery, he is more than willing to sleep with Cathy on his brother’s wedding night. Although Charles is aware of Cathy’s manipulative nature, he nonetheless gives into temptation and follows the impulse toward evil rather than good.