The central conflict in To Kill a Mockingbird has been established. The gravity of the situation, of Atticus' decision to defend Tom Robinson against the charge of raping a white woman was clear. It is in this chapter, however, that Lee presents one of her most crucial scenes: the act of Atticus facing down the hostile mob gathered outside the jail to lynch Tom. Lee’s use of language to establish the atmosphere occurs right away. After resolving a conflict involving Dill, Scout notes: “A nightmare was upon us.” Chapter 15 is not about Boo Radley, or Jem, Scout and Dill whiling away the hours, or even about Atticus’ continuous defense of his decision to represent Tom. This is the chapter in which Atticus’ decision is placed in a life-and-death context, and Lee’s language leaves little doubt regarding the peril with which Jem and Scout view developments. The plot regarding Tom and his upcoming trial has been leading to some kind of climax, and, as Atticus and his children relax after supper, the sense of foreboding alluded to earlier begins to take shape:
There was a knock on the front door, Jem answered it and said it was Mr. Heck Tate. ‘Well, ask him to come in, said Atticus.
“I already did. There’s some men outside in the yard, they want you to come out.”
In Maycomb, grown men stood outside in the front yard for only two reasons: death and politics. I wondered who had died. Jem and I went to the front door, but Atticus called, “Go back in the house.”
In this scene, Lee uses the proverbial nighttime “knock at the door” to build suspicion – suspicion that bad things were about to occur. The presence of the group of men outside on Atticus’ porch is initially threatening. While Lee establishes that these men are known to Atticus, and not generally to be feared, there is still a palpable tension as Scout describes the evolution of the scene:
“There was a murmur among the group of men, made more ominous when Atticus moved back to the bottom front step and the men drew nearer to him.”
The use of the word "ominous" suggests suspicion and fear. As Lee establishes the identities of these men as friends and neighbors who do not represent a threat, however, she alludes to one still looming, that of “that Old Sarum bunch." Suspicion is now being replaced by fear. The Sarum bunch, as Atticus expected, arrives at the jail intent on lynching Tom. The scene that follows is described by Scout as follows:
In ones and twos, men got out of the cars. Shadows became substance as lights revealed solid shapes moving toward the jail door. Atticus remained where he was. The men hid him from view.
“He in there, Mr. Finch?” a man said. . .
“You know what we want,” another man said. “Get aside from the door, Mr. Finch.”
Much of the chapter involves Lee’s use of language to build suspicion and fear. Her use of language to convey innocence involves Scout’s searching of faces in the mob:
"I sought once more for a familiar face, and at the center of the semi-circle I found one."
This innocence is illustrated as she attempt to engage Walter Cunningham in a discussion regarding his legal affairs and his son, a former classmate of Scout’s.
Walter Cunningham is one of the members of a mob intent on killing an innocent man in defiance of the law. The men confronting Atticus in front of the jail mean business. Scout’s entreaties to Cunningham demonstrate her enduring innocence.