What is the theme in The Monstrumologist by Rick Yancey?

One of the most poignant themes in the novel is the leaving behind of the past in an effort to move forward. Will Henry lost his parents in a fire, and suffers greatly as a result. He misses them terribly, and in addition, he has an affliction, readers learn at the end, that stems from his own father. The worms that have infected him were, in a way, the cause of his father and mother's death. Further, it is because of their death that he is in the care of Dr. Warthrop, as he has no other family or friends to care for him.