Scout is missing Dill, who has returned to Meridian, as she retells the story about how Atticus told Tom Robinson's wife, Helen, about his death. Jem and Dill were walking home from Barker's Eddy, where Jem had finally taught Dill to swim, when Atticus passed them in his car. Atticus told them that they would need to continue walking, since he and Calpurnia were busy and wouldn't be going home for a while. When "Jem protested, then pleaded," Atticus agreed that they could come along, under one condition.
"All right, you can come along with us if you stay in the car." (Chapter 25)
The boys stayed in the car as they were told, where they watched Helen fall
"... down in the dirt... like a giant with a big foot just came down and stepped on her... Like you'd step on an ant." (Chapter 25)