Murder Through the English Post — Jessica Ellicott

A rash of poison pen letters has enveloped the sleepy English village of Walmsley Parva in cloud of suspicion and paranoia. But when rampant aspersions culminate in murder, enquiry agents Beryl Helliwell and Edwina Davenport must stamp out the evil-minded epistles . . .

What began for two dear if very different friends -- an American adventuress and a prim and proper Brit -- as a creative response to the lean times following the Great War has evolved into a respectable private enquiry business. So much so that Constable Gibbs calls upon Beryl and Edwina to solve a curious campaign of character assassination.
 
A series of anonymous accusations sent via post have set friend against friend and neighbor against neighbor. In her new position as magistrate, Edwina has already had to settle one dispute that led to fisticuffs. Even Beryl has received a poison pen letter, and while she finds its message preposterous and laughable, others are taking the missives to heart. Their headstrong housekeeper Beddoes is ready to resign and one villager has attempted to take her own life.
 
The disruption of the peace goes far beyond malicious mischief when another villager is murdered. Now it's up to the intrepid sleuths to read between the lines and narrow down the suspects to identify the lethal letter writer and ensure that justice is delivered . . .