Poison in the Pen (Miss Silver #29)
by Patricia Wentworth
A series of cruel letters upends life in a small village, and Miss Silver searches for the anonymous scribe.
It is through her friend Frank Abbott, of Scotland Yard, that Miss Silver first learns of the anonymous letters. A widowed cousin of his, living in a small country village, is being tortured by an unknown author who insinuates that the young woman’s husband may not have died of natural causes. It is a case of the kind of cruelty that is all too common in the countryside, and the governess-turned-detective listens with only polite interest.
Then the first death comes. Another target of the letter-writing campaign, tortured by the threats to reveal her darkest secrets, drowns herself in the manor-house pond. The Yard sends Abbott to unmask the sinister letter-writer, and he brings Miss Silver along as an undercover agent, masquerading as a tourist as she attempts to stop the next death before it happens.
Miss Silver Mystery #30