From the blog Classic Mysteries: "The little English town of Cotten Abbas is being plagued by someone who is sending anonymous poisoned pen letters to people in the town. Letters of this type usually accuse the recipient either of some crime or of some major breach of morality. If there is any degree of truth in the letters, they can be deadly, and they would appear to be the reason behind at least one death in Cotten Abbas. The mysterious Mr. Datchery, newly arrived in Cotten Abbas, rather clearly knows more than he is saying about the letters and their source. But it will become a case of murder that will puzzle Crispin’s detective, Oxford Professor Gervase Fen, though he’s not even mentioned to us by name until more than two thirds of the way into the novel. It's a good thing that he’s on hand too, as the evidence looks remarkably black against one of the town's two doctors, Dr. Helen Downing, the sympathetic heroine of the book. It would appear that someone is trying to frame her for a murder that is most likely connected to the poisoned pen letters. And that someone is doing so quite effectively until Fen comes along.

I don’t want to say much more about the plot – it’s quite typical of Crispin, enormously complicated, between the poisoned pen letters, the suicide by a recipient of those letters, and the murder of a young teacher which – according to the evidence – could only have been committed by Helen Downing. And the facts seem to be so damning that even the investigating police officer – who has fallen in love with Helen Downing – finds himself suspecting her of murder."