The Weed That Strings the Hangman's Bag- Alan Bradley

When a mysterious puppet show arrives in Bishop's Lacey, death is not far behind... a grisly murder during a performance of Jack and the Beanstalk in the village hall reaches back to an earlier crime that has cast a shadow over the village for years. Flavia's investigations test her powers of deduction to the limit - and provide a shocking insight into the darker corners of the adult world.