Murder in the Mill-Race by E. C. R. Lorac
Murder in the Mill-Race, also published as Speak Justly of the Dead, takes place in a small, somewhat isolated town North Devon. Dr. Ferens has taken over the practice of the mostly retired town doctor and he and his wife are happy to move away from the grit and grime of the city. Of course, villages come with their own sets of difficulties, and in this particular village, one of those is Sister Monica who runs the children's home. Mrs. Ferens has an instant dislike to her and while the townsfolk all praise her, you know something's not quite right. It's no surprise when she ends up dead in the stream just beyond the mill.
We meet the people in town as Dr. Ferens does and we are allowed to settle into the setting nicely before the murder occurs. Even then the local guy does a bit of investigating before MacDonald is called in. The villagers are not keen on answering...