A visit to The Rue Morgue, scene of the crime, not where autopsies happen
Details
This time around, look to Edgar Allan Poe's first story with his detective, C. Auguste Dupin appearing in The Murders in the Rue Morgue. One of his Tales of Ratiocination.
I'll give you a hint. The Butler did not do it.
Free copy of Murder in the Rue Morgue from Project Gutenberg.
https://www.gutenberg.org/files/2147/2147-h/2147-h.htm#chap07