As Chimney Sweepers Come To Dust- Alan Bradley

When Flavia de Luce is banished to Miss Bodycote's Female Academy in Canada she's soon on familiar ground, when, on her first night, a mummified body is dislodged from a chimney, and she is presented with a gruesome puzzle to solve. Girls have been disappearing with alarming regularity, leading Flavia to wonder not only how and why, but what exactly is the academy's true purpose? Flavia must enter a shadowy world where truth and lies seem interchangeable and no one can be trusted.