Another of the author's vampire Judge Dee and his human assistant mystery stories, this one has the pair in Paris, when the Judge encounters an old adversary he has been after for crimes against other vampires (humans too, but they don't count to Judge Dee).

But when they, the adversary and other vampires gather for a party, something horrible happens to the adversary, and Judge Dee must now determine the course of events and pass judgement.

If you paid close attention to the story, you may have figured out who is the suspect and the motive.