Poison expert, deductive genius and lovable busybody Flavia de Luce returns, wending her way down a river and straight into a twisty mystery that may just send her to an early grave. In the wake of family tragedy, twelve-year-old Flavia de Luce finds herself facing a summer with a lot of time on her hands and not much to do. When Dogger, the loyal family servant, suggests a boating trip for Flavia and her reluctant sisters, Flavia obliges. Travelling down the river, she contemplates the recent spate of murders by a church vicar who poisoned three of his female parishioners with cyanide. But when Flavia dips a languid hand in the river, her thoughts are halted when her fingers grasp something. Expecting to have a hold on a fish, the river instead yields Flavia a dead corpse—much to her delight. What better way to while away the time than to solve a juicy mystery (or two)? But the case seems to involve a motley cast of suspects. After all, what could connect the son of an executed killer, a far too canny police constable, a travelling circus, and the publican's mysteriously talented wife? As she works to find answers, Flavia will need to keep her wits about her, or risk falling into a watery grave of her own.