Aslan, thank you for your help!!!! Another question: What was the best kept secret about the children's father?

Hey! I think that you are referring to when Atticus shoots Tim Johnson, the rabid dog. This takes place in Ch. 10 on pg 96 (in my copy). Atticus turns out to be an expert shot with a rifle. Jem and Scout are so surprised. Mr. Tate tells them that they used to call Atticus "one-shot Finch."