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

Scout's appeal to Mr. Cunningham softens the men and makes them extremely uncomfortable. She mentions his entailment, as well as the fact that his son Walter is a "friend". Scout's innocence seems to bring Mr. Cunningham to his senses, she appeals to Cunningham's humanity rather than his hate. Mr. Cunningham tells the mob to go home.