In the brilliant novel by Ellen Raskin (Westing Game) there are several themes that shine through. First it is that people are not always what they seem. This is played out by the end of the first chapter, even, when it is very clear that some of the tenants are lying. This sets everything up perfectly for the deeper theme of finding hope, breaking through barriers, and finding common ground to accomplish a goal. It also reinforces the idea that when you rush to judgement that it can backfire on you.
