How does Tom Robinson's death and false accusation help illuminate the meaning of the work as a whole?

I'm trying to break down this prompt question. Any help? :

The most important themes in novels are sometimes developed in scenes in which a death or deaths take place. Write a well-organized essay in which you show how a specific death scene (Tom Robinson) in "To Kill a Mockingbird" helps to illuminate the meaning of the work as a whole. Avoid mere plot summary.