Everybody leaves Max and Mame's house except for Christmas, who is still lying on the floor. He eventually manages to get up and get out of the house, and for the next fifteen years he essentially lives on the road, going from city to city, and finally ending up in Jefferson, Mississippi. While on the road he works many different jobs and sleeps with many different prostitutes, often telling them that he is black so that they will kick him out without asking him to pay. One time when he attempts this in a city farther north, the prostitute does not care, and he is so disgusted by the idea that a white woman would sleep with a black man that he beats her almost to death.
For two years after the incident with the white prostitute he is driven crazy by it, intentionally goading white men into beating him up for his race. He goes to live among the black population of Chicago and Detroit, shunning white people. He keeps moving, never able to remain in one place for long, until eventually he arrives in Jefferson. He finds Joanna Burden's house, watches it until the lights go out, and then sneaks inside to try to steal some food. He finds peas in the kitchen, but Joanna comes down and finds him while he is chewing away. Thus begins the relationship between Christmas and Joanna. They talk little, and often act like they are strangers even after they have started sleeping together. She makes him food regularly, but never stays in the kitchen while he eats it. He keeps living in the cabin on her property, but she leaves the back door open at all times so that he can enter and come to her bedroom whenever he likes. One night Christmas expects Joanna to have locked him out, but when he tries the door he finds it open. He goes into the kitchen and finds a meal that Joanna laid out for him. He slowly and methodically smashes it against the wall.
After the incident with Joanna he starts to work at the mill, and does not go back to the house for six months. When he finally returns, he finds Joanna sitting on his cot waiting for him, and she tells him her life story. Her grandfather, Calvin Burden, tried to teach his children to hate hell and slavery. Her father Nathaniel Burden ran away from home at fourteen, fell in love with a Spanish woman, and finally came back home with a twelve-year old son, also named Calvin Burden. Calvin was Joanna's half-brother who was killed fourteen years before she was even born, when he was twenty, because he believed black people should have the right to vote.
After his wife, father and son have died, Calvin sends for a new wife from New Hampshire. Joanna's mother travels to Jefferson, and the two marry on the day of her arrival. Joanna is born two years later. All that Joanna remembers of her father is the burden he gave her of believing that every white man is doomed by the curse that God put on the black man. After Joanna tells all of this to Christmas, he tells her again that he knows nothing about his parents except that he is part black. She asks how he can know this, and he says that he doesn't, suddenly realizing that he has lived his whole life based only on an unproven assumption.
After this the relationship enters a new phase, with Christmas working at the mill and Joanna meeting with the black people she helps during the day. Each night Christmas eats the meals Joanna prepares for him by himself before going to bed with her. Joanna becomes more and more wild in bed, and in Christmas's eyes becomes more and more corrupt, although it is not he who is corrupting her. He watches the struggle of the two Joannas-one calm, religious and man-like, the other passionate, jealous and depraved-and sees that he should leave, but somehow he cannot bring himself to do so.
During this time Christmas starts to sell whiskey on Joanna's property, but discretely and without telling her-more out of the need to conceal something than for fear of her disapproval. Joanna starts to suffer bouts of insomnia because she senses that she will soon be saved, but that does not calm her, as she wants to continue in her depravity. Joanna starts to talk to Christmas about having a baby, but he has no interest in giving up his freedom. A few months later she tells him that she is pregnant. Christmas believes she is lying until he sees her face.
Christmas plans to run away, but again he finds himself putting off his exit and avoiding Joanna for months. She finally leaves a note for him to come see her, and when he does she refuses to sleep with him and does not mention the baby, but instead tells him that she wants him to take over all of her work, and that she will act as his assistant. He avoids her again for months, during which time he starts working with Joe Brown, and invites him to live in the cabin with him. One night Joanna finally leaves another note for Christmas, and when Christmas goes to the house Brown follows him. Christmas strikes him a few times, and Brown runs away.
When Christmas goes up to Joanna's room, she tells him she wants him to go to a black college, and then to learn law from her black lawyer, so that he will be able to handle her money and her affairs. In his anger, Christmas suddenly sees how old Joanna is; he realizes that she was never pregnant, but actually has gone through menopause. The next time she orders him to come she gives up on sending him to college, but has gone into a religious frenzy and tries to save his soul. When it becomes clear that he refuses to be saved and will not even kneel with Joanna while she prays, she decides that they must die together. The next night when Christmas goes to her room, he brings a razor to kill her, but when he refuses to pray she draws a gun. When she pulls the trigger, the chamber does not explode, and so he kills her with his razor.
This section of Light In August complicates many of the previously established themes in its layered depiction of Christmas's relationship with Joanna Burden. Up to this point in the novel Christmas has exhibited violence against women multiple times, and this culminates in his murder of Joanna. And yet the causes of her death are far more complicated than Christmas's misogyny. First of all, her murder is not committed with the same blind, inexplicable rage that usually comprises his violence, especially against prostitutes. Secondly, Joanna is only partially a feminine figure.
During the second phase of their relationship, Joanna is depicted as having two wholly distinct parts. One part is her public persona: she is a middle-aged single woman who has lived in deep seclusion for almost all of her life, with the exception of the black people whom she takes care of, and who care for her in return. This half of Joanna is presented as completely independent, calm, and unemotional, and thus rather male. The narrator in fact repeatedly uses male adjectives to describe her, often distinguishing between Joanna and any other woman Christmas has ever known. The other half of Joanna is her "night" personality-wild, lustful, conniving, and, according to Christmas, very feminine. Christmas's perception of and reaction to these two personalities only increases the ambiguity of the gender roles in the novel. At times he seems disgusted by the feminine side, and yet he also seems mystified and somewhat threatened by the male side. What does say a lot about Christmas's understanding of gender is the fact that he so linearly connects the two aspects of her personality with male and female.
The question of race further complicates the relationship between Christmas and Joanna. Joanna is not disgusted by the secret of Christmas's race as Bobbie is, nor is Christmas disgusted by her lack of disgust, as he was with the prostitute that he almost beat to death. Yet Christmas does seem put off by any attempt Joanna makes to better his situation or take care of him, seeing these efforts not as kindness, but as displays of condescension. And in fact it is hard to know whether that is the case or not, as the aptly-named Joanna Burden is obsessed with the South's burden of a violent racial history.
Her father told her that the black man is the white man's doom, and that no one can escape it. Her belief in this clearly dictates the way she lives her life, and thus may be closely tied to her relationship to Christmas. It is not surprising that Christmas's belief that this is the case ultimately pushes him to kill her, since he is dangerously obsessed with his own race and the effect it has on his relationships. What is surprising is that he remains in the relationship with her for so long. It is really the relationship itself, and not its violent end, that complicates the issues of race and gender in the novel.