When Sally needs a specific book for a school report on trees, she finds it?s overdue at the Busytown Library and the Librarian can?t read who took the book out because of a mysterious green drip covering the name. The only letter in the signature they can make out is the letter V. But that?s enough to get Huckle, Lowly and Sally on the road to solving the Borrowed Book Mystery and finally deducing that the drip is green paint from none other than famed Busytown artist Vincent Van Goat! The Busytown Bookshop is missing a new delivery of 'Molly Mystery' books. Huckle and his friends search unsuccessfully for the box marked with double 'M's. After seeing how an upside-down number six can be mistaken for a nine, the kids check a box bearing a pair of 'W's and find the missing mystery books.