What suspense does Lee create for the reader in this chapter?

I think Scout's showdown with Francis finally happens. Although she has promised not to fight, Francis just proves too offensive and annoying to resist taking a swing. After dinner, Francis and Scout are outside in the backyard. Francis says that Atticus is a "nigger-lover," and that now Atticus will be the ruination of the family, who won't even be able to walk the streets of Maycomb. Scout patiently awaits her chance, and then punches him squarely in the mouth.