I'm not sure I understand your question, but I assume you are talking about the group of citizens who attempt to release Tom Robinson from the jail in Chapter 15 of To Kill a Mockingbird.
Atticus is warned about this possibility at the beginning of the chapter when a group of concerned neighbors visits him at his house. Jem and Scout only hear part of the conversation, but they realize it is something serious since
In Maycomb, grown men stood outside in the front yard for only two reasons: death and politics. I wondered who had died.
Link Deas tells Atticus that it is " 'that Old Sarum bunch I'm worried about.' " Later, inside, Atticus mentions the Ku Klux Klan, and Scout seems to know a little about the group from a previous altercation in Maycomb. Scout seems mostly clueless about the earlier meeting, but Jem tells her that " 'I'm scared.' " When the children meet up with Atticus at the jail the next evening, she sees that most of them are "strangers"--"cold-natured" and dressed in overalls. But she does recognize Mr. Cunningham--Walter Cunningham's father. She knows that most of the Cunninghams are farmers who live in the country outside the city limits. She innocently engages him in a conversation, and the men eventually leave. She has no idea that they are a lynch mob bent on freeing (and then probably hanging) Tom Robinson, and that her little talk with Cunningham may have saved Atticus from taking a beating--and Tom's life as well.