CECIL CASTELLUCCI: The other thing is that I'm very interested in theme. So my theme that I find, that I go to over, and over, and over again is how do we find our tribe, how do we find our true tribe of friends, our true tribe of people that we can go to? How do we become who we are? And I think that as a person who writes young adult literature, that's the essential existential question that we have as young people, teenagers have, like who am I, what kind of a human being am I going to become? And so that's sort of the grain of sand that makes the pearl for all of my books.