The Westing Game.
Pic from: ccbc.education.wisc.edu
I think that this is important because here it shows that Theo wants to be as helpful as possible, and he is very optimistic.
Second Key Passage
I think that this plot part is important because Theo knew who the bomber was, and if Theo knew everybody knew. Later, the next page also shows how Theo is really a good guy by not trying to blackmail Angela.
Theme song describing character.