Everyone's favorite, totally amazing, super sleuth-y detective is back to tackle more perplexing problems and mysterious mysteries. Mariella knows that all good detectives write down important information about their investigations, so she records everything in her top secret journals: important clues, observations, tons of drawings, and advice for new detectives. She also knows how important it is to surround herself with other budding detectives to learn new and exciting ways to crack cases. In The Mystic Mustache, Mariella and the Mystery Girls are at a Young Super Sleuth convention when they notice some super strange stuff going on. Could it be related to the mysterious Mystic Mustache? Kids who enjoyed Diary of a Wimpy Kid, Dork Diaries, and Clarice Bean books will want to tag along as Mariella uses all of her brain power (and girl power) to solve this hairy mystery.