This novel takes place after Diamond's return to Bath, while he is trying to settle in with his new team. It features a valuable stamp, a locked-room murder mystery and a circle of crime fiction aficionados calling themselves the Bloodhounds of Bath.
I like this one a whole lot better than The Summons. I found it better crafted, and the far-fetchedness of the plot in some instances matched the theme of the book, which is the discussion of preposterous crime stories. After reading this I'm going to try to read some more of John Dickson Carr; I have read a bit, but not much.