The immediate thing that jumped into my head, which was actually an idea that I had a LONG time ago and never took anywhere, was gargoyles that turn into people. At night. And run around causing havoc. And maybe the boy sees them and doesn't realize what they are and wants to join them or something...if you like cities, you could definitely go somewhere with that. Like, guardian gargoyles of the city, heh heh. Except for the havoc-wreaking. :D

...wow, stream-of-consciousness is fun!