Author Harper Lee links the first and last chapters together through the events of the ill-fated Halloween night and the man who saves their lives--Boo Radley. The opening paragraphs of the novel are a retrospective look back from many years in the future: Jem is healed and has been able to fulfill his dream of playing football. Atticus is still alive, and his children still go to him when they need to "settle an argument." Chapter 1 serves as exposition for both past and future events: After Scout gives the reader a glimpse of the future, she recounts the distant past, exploring the Finch family history, the arrival of Dill, and the mysteries of the Radley family. In the final chapter, Lee ties together the two main plots of the story--that of Boo Radley and how he avenges Tom Robinson's death by killing Tom's accuser, Bob Ewell--before Atticus settles down to watch over his injured son for the night. Life goes on for the Finch family, and as Jem and Scout grow older, they argue about the causes of that memorable Halloween night.
I maintain that the Ewells started it all, but Jem... said it started long before that... when Dill first gave us the idea of making Boo Radley come out. (Chapter 1)