What persuades the lynching-party to give up their attempt on Tom's life?

Scout and Jem's appearance at the jail certainly ruffles the feathers of the men, who are determined to take Tom Robinson from the jail and dole out their own form of justice. None-the-less, it is Scout who makes the event personal when she approaches Mr. Cunningham to ask abut his family, which in turn, makes all the men uncomfortable. Scout's intervention and attempt at conversation is directly responsible for the men's dispersion.