It was Dill's last day in Maycomb before leaving for his home in Meridian, and Jem had discovered earlier "with angry amazement" that Dill had never learned to swim. So, after two afternoons of practice, the two boys made their plans to go to Barker's Eddy, where Jem hoped to finish his lessons concerning this essential necessity of life. Scout was not invited, since "they were going in naked, and I couldn't come." Instead, Scout would help Aunt Alexandra with her Missionary Circle tea.
Atticus made a surprise visit to the tea.
His hat was in his hand, and his face was white.
He broke the news to Aunt Alexandra, Miss Maudie and Calpurnia: Tom Robinson had been killed. He had come to ask Calpurnia to come with him to see Tom Robinson's wife.
In the opening of Chapter 24 of Harper Lee's To Kill a Mockingbird, Scout explains to the readers that, on Dill's last day in town for the summer, shortly after Tom Robinson's trial, Jem had decided to teach Dill how to swim at the local swimming hole called Barker's Eddy. Jem had been teaching Dill for the past two afternoons. In addition, Scout informs us that "they said they were going in naked and I couldn't come"; therefore, being a girl, Scout is forced to remain at home with the female role models in her life: Calpurnia, Miss Maudie, and Aunt Alexandra.
Scout's inability to accompany her brother and Dill in Chapter 24 marks a real turning point in Scout's maturity and self-discovery. Throughout the novel, Scout had been torn between wanting to be a tomboy and the fact that she is a girl expected by society to play a certain role. However, on that particular day, since she cannot accompany the boys, Scout is inclined to accept her aunt's invitation to join the missionary circle for refreshments and does so dressed in her Sunday best. This moment, coupled with Atticus's sudden appearance, looking white with shock, serves as a true moment of awakening for Scout: she finally learns to appreciate exactly what it means to be a lady.
Atticus comes home early, interrupting the missionary circle meeting, with hat in hand and face looking white because he has just learned that Tom Robinson has been shot to death while trying to escape prison. Atticus's face is white because he is upset on two different accounts. First, he is upset that Robinson gave up on Atticus's attempts to free him through appeal and instead decided to take justice into his own hands by attempting to escape prison. Second, he is upset because, though he knows the prison guards fired a warning shot, he is shocked to learn that Robinson was shot 17 times. Atticus expresses his distress to Aunt Alexandria, Miss Maudie, and Calpurnia in the kitchen when he says, "Seventeen bullet holes in him. They didn't have to shoot him that much" (Ch. 24).
Aunt Alexandra and Miss Maudie are equally upset by the news; however, Scout is surprised to see that they forcibly pull themselves together enough that they can return to their company with smiles on their faces. On this day, rather than swimming with the boys, Scout develops, through observing her female role models, the understanding that to be a lady requires a great deal of bravery. More specifically, putting on a brave face in moments of adversity in order to continue to show respect to others, such as guests, requires the utmost bravery and is what being a lady is all about. Scout expresses this epiphany and her newfound desire to be a lady towards the end of the chapter:
I carefully picked up the tray and watched myself walk to Mrs. Merriweather. With my best company manners, I asked if she would have some. After all, if Aunty could be a lady at a time like this, so could I. (Ch. 24)
Hence, Scout's inability to join the boys leads her to develop new understandings about who she is as a girl.
Poor Scout! With as much fun as she has being a tomboy and running around with the boys all summer long, she's still a girl, and therefore isn't allowed to go skinny-dipping with them. The boys probably told her they were "going in naked" just to keep her away. By chapter 24, though, Scout is older and maturing. In fact, she's going into the third grade, which makes her around 8 years old. Aunt Alexandra is hosting one of her missionary teas that day as well, which is a perfect time for Scout to put on a cute little dress and join the party.
After the missionary business is over, Aunt Alexandra invites neighbors over for refreshments. It's during this tea party that Atticus comes home unexpectedly early and Scout notices that his face is white. As he goes into the kitchen to speak with Calpurnia, Scout goes in and overhears what's going on. Atticus needs Cal to go with him to Helen Robinson's home to inform of the following:
"Tom's dead. . . . They shot him. . . . He was running. It was during their exercise period. They said he just broke into a blind raving charge at the fence and started climbing over. . . . They fired a few shots in the air, then to kill. They got him just as he went over the fence" (235).