Speaking from Among the Bones (Flavia de Luce #5) by Alan Bradley

Eleven-year-old amateur detective and ardent chemist Flavia de Luce is used to digging up clues, whether they’re found among the potions in her laboratory or between the pages of her insufferable sisters’ diaries. What she is not accustomed to is digging up bodies. Upon the five-hundredth anniversary of St. Tancred’s death, the English hamlet of Bishop’s Lacey is busily preparing to open its patron saint’s tomb.