How does Atticus stop a lynching (in Chapter 15)?
It is not Atticus so much who stops the probable lynching of Tom Robinson as it was the sudden appearance of his children at a crucial moment. Atticus knew that Tom would be housed in the local jail for a night or two, and he also knew that there might be trouble from a segment of the local townspeople. When Sheriff Tate was called out on a "snipe hunt," Atticus headed to the jail to stand guard. Sure enough, several carloads of locals showed up with the intent of taking Tom Robinson from the jail with them (no doubt for a beating and hanging). Just as the men were about to push past Atticus, the three children--Jem, Scout and Dill--showed up. Although they saw that Atticus did not seem to be himself, they did not understand the seriousness of the situation. Scout immediately said hello to Walter Cunningham, father of one of her schoolmates. Her innocent chitchat with the would-be murderers eventually shamed them into realizing that they could not carry out their plan in front of innocent children.