Get a Clue! (Lizzie McGuire Mysteries, No. 1)

Someone has been leaving creepy notes in lockers, notebooks, and knapsacks all over school, with messages like "I Know What You Did Last Week." Students are getting really annoyed. And the notes all appear to be written by one person-Lizzie McGuire! But who would want to frame Lizzie for such a totally bizarro prank? Time for Lizzie to track down the guilty party before she's exiled to Loser-ville forever!