Who is Paul Leonard from Welcome to the Monkey House and what is their importance?

An eight-year-old boy, Paul is being left home alone for the first time. It doesn't seem very important to him at first. He plans to look at his microscope. He is not afraid and seems almost amused by his parent's agitation. However, Paul becomes very frightened listening to the fight in the next apartment, until at one point, he is genuinely afraid that the people fighting will kill each other.