Carroll & Graf (1989)
It is carnival time in New Orleans in 1858. But her Majesty's Consul, Dick Macrae, isn't feeling very frivolous. In fact he is much disquieted by a sense that he is being followed - that all is decidedly not well. Then a visit by Madame de Sancerre, a Creole beauty, and her even more famously beautiful daughter sets in motion events that rapidly lead to a corpse.
Peopling his story with historical characters, John Dickson Carr has evoked all the lush charm and danger of the New Orleans of more than 100 years ago and used this setting as the backdrop to an "impossible" puzzle that comes clear only when the solution is revealed.