When this peculiar ad appears in the newspaper, dozens of children enroll to take a series of mysterious, mind-bending tests. (And you, dear reader, can test your wits right alongside them). But in the end just four very special children will succeed. Their challenge: to go on a secret mission that only the most intelligent and resourceful children could complete. With their newfound friendship at stake, will they be able to pass the most important test of all? Формат издания: 13,5 см х 19,5 см.