Some unspecified amount of time later, Celie asks Squeak why Harpo is moping, and Squeak replies that Sofia has been thrown in jail, and Harpo is upset. Before she begins to tell the story, Celie tells Squeak to make Harpo call her by her real name, Mary Agnes, since that will force him to respect her.
Celie understands that Squeak's real name is a source of power for Squeak. If Harpo calls her Mary Agnes, he is recognizing that she is a person, one whose feelings matter.
The story goes as follows: Sofia, Buster, and Sofia's children were walking around downtown, when they ran into the (white) mayor and the mayor's wife. The mayor's wife complimented Sofia on her children's pretty faces and "white teeth" and asked whether Sofia would want to serve as maid to the mayor's household, since she apparently did such a good job raising her own children.
Sofia, once again, brooks no insults from anyone. Of course, she knows that her resistance here will only land her in trouble, but she feels it is more important to stand up for herself, whatever the consequences may be, than to kowtow to white authority.
Sofia said "hell no" to this offer; when the mayor asked her to repeat herself, and she did, he slapped her for her impudence, and Sofia fought back, knocking the mayor down. Buster restrained himself, though he wanted to defend Sofia, because he knew that if he were to intervene, he would be shot by the police. And, indeed, the police were quickly called to the scene to break up the fight to protect the mayor and his wife.
Again, Buster avoids confrontation, and ends up being instrumental in helping to raise Sofia's children while she is in prison, and later, when she serves as maid to the mayor's children. Sofia is one of the novel's unluckier characters—although she has attempted to gain her freedom from Harpo, she ends up losing her freedom entirely, and is placed in jail.
Mr. ____, who is on friendly terms with the white sheriff, convinces that Sheriff to let him visit Sofia. He goes to the jail to do so, and eventually convinces the Sheriff to let Celie visit as well. Celie, when she visits later, combs Sofia's hair and is horrified by how battered and bruised she is; Sofia has been beaten by the police almost beyond recognition.
Sadly, Mr. ____ has come to know the sheriff because Bub has spent so much time in and out of prison. Mr. ____'s concern for Sofia, here, is another indication that he does care about the wellbeing of other people—but not, at this point, about Celie's wellbeing.