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. Nobody is more excited to peek inside the crypt than Flavia, yet what she finds will halt the proceedings dead in their tracks: the body of Mr. Collicutt, the church organist, his face grotesquely and inexplicably masked.

Who held a vendetta against Mr. Collicutt, and why would they hide him in such a sacred resting place? The irrepressible Flavia decides to find out. And what she unearths will prove there’s never such thing as an open-and-shut case.