Will Allen may be small, but he's one of the smartest boys in the 5th grade at Ashford Middle School. Too bad being very clever does him no good when monsters begin haunting him! It's lucky that he can trust his best friend Jeannine to believe him, because his parents just don't take him seriously. Together, Will and Jeannine search for help, but they get nowhere until a strange business card appears in Will's book bag, instructing him how to summon Bigelow Hawkins, the Great Monster Detective. With Bigelow's help, along with the use of a very special flashlight and magnifying glass, Will must learn how to conquer the monsters and uncover the secret of the dreadful HIDDEN BEAST before it's too late...