The Biblical story of Cain and Abel, the sons of Adam and Eve, provides the narrative framework of Steinbeck's novel. East of Eden demonstrates the perpetual conflict between good and evil in each character. The plot is essentially a recurrence of myth of Cain and Abel. However, in the novel each character seems to resemble one of these two brothers. Charles and Adam, sons of the well-known Cyrus Trask, correspond to Cain and Abel, in the novels first iteration of the biblical story.
In the Bible, God sparks Cain's jealousy by preferring Abel's sacrifice of a fine lamb to Cain's sacrifice of grain. This enrages Cain, and he becomes jealous of his older brother. This leads Cain to kill his brother out of enraged anger. In a parallel in East of Eden, Cyrus Trask sparks his younger son Charles's jealousy by preferring his older sons' gift of a puppy to Charles's gift of a knife. After hearing this, the young Charles proceeds to severely beat his brother out of anger. This is the beginning of the difficult relationship between the two brothers. We learn from the beginning that Adam is kind and good-natured, while Charles is violent and manipulative. As the novel continues, we learn more and more about the vast differences between the two brothers. Charles becomes increasing cynical and obsessive. Adam continues to be idealistic and faithful. Towards the end of chapter 9, Steinbeck introduces the most important character in the novel, Cathy. Cathy is the epitome of evil, who as a young girl murdered her parents by an arson attack. Cathy is introduced to Adam Trask when she stumbles on upon his home battered and bruised after a fight with a man in charge of prostitutes. The good-natured Adam immediately helps her and cares for her tenderly. Not knowing her behavior, Adam begins to like Cathy. Adam proceeds to ask Cathy to marry her and Cathy who considers the safe harbor that the marriage would provide, accepts.