Throughout the book the carnival is associated with nothing but bad deeds and awful events. It is a place of evil run by evil people. The carnival is not a part of the town, so its evil is something beyond the normal evil in man. In fact, its evil may be viewed as the evil that threatens to destroy towns. The carnival is the evil that drives people apart and unites them through fear and manipulation, rather than through freedom and caring. The carnival is the evil that threatens to make all people selfish and greedy, and it must be combated in order to ensure that there will always be communities of people living together in harmony.
Young boys run where they will and act upon passing fancies. So, in Something Wicked This Way Comes, does life. Things occur unexpectedly and pop up out of nowhere, just like the young boys who run everywhere and can be anywhere at any given moment. The unpredictability of young boys is matched only by that of life. Part of the reason that Jim and Will may have been the ones to figure out the carnival is that, while they did not anticipate it, they move with it. They see it arrive and see it end, because they move fast enough and far enough to see many things. The other people in the town are a step behind, and they are no match for the carnival. Will's father, on the other hand, gets in touch with his youthful side just in time to put and end to the carnival. The three run together at the end of the book, just as life in Green Town turns a new page.