In chapter 15, Atticus leaves the house late at night and the children—finding this behavior out of the norm—decide to follow him. From across the street, they watch him as he sits in a chair reading the newspaper outside of the Maycomb jail. Just as they are about to leave, several carloads of men pull up in front of the jail.
Scout thinks the group is comprised of people she knows and crosses the street to join Atticus and the group. When she jumps into the middle of the group, Scout is filled with embarrassment to find that it is a group of people she does not know. She notices a look of fear on Atticus's face. While Scout does not understand why these men have shown up, Atticus does. The mob of men have come to take Atticus's client, Tom Robinson, out of the jail and kill him prior to the trial even starting.
Scout desperately tries to cover her embarrassment by finding a familiar face in the group. She recognizes the face of Mr. Walter Cunningham, who was previously a client of Atticus's and who is also the father of one of her classmates. Scout begins by talking to Mr. Cunningham about the previous legal matters with which Atticus had helped. Mr. Cunningham does not acknowledge her, so she switches the topic of conversation to something else she thinks may interest the man—his son. Mr. Cunningham finally nods at Scout but does not verbally respond. Feeling like she isn't doing a good job of engaging the man in conversation, Scout switches back to talking about Mr. Cunningham's "entailment."
Finally, Mr. Cunningham responds to Scout when he says, "I'll tell him you said hey, little lady." It is at this point that Mr. Cunningham addresses the rest of the mob and says, "Let's clear out." The men listen to Mr. Cunningham and get back into their cars to depart, leaving Tom Robinson, once again, safe.
At breakfast the next day, Atticus explains to the children how Scout's conversation forced Mr. Cunningham to stand in Atticus's shoes and consider his perspective.
That proves something—that a gang of wild animals can be stopped, simply because they're still human. Hmp, maybe we need a police force of children... you children last night made Walter Cunningham stand in my shoes for a minute. That was enough. (Lee, 157).