There is no mouse Y axis invert in first-person perspective (aka "Pilot Mode") in Sherlock Holmes: Nemesis through the menus. I Googled for a solution but nothing was posted... there were "solutions" of installing scripts/code to do it when the Alt key is held etc., but I found that this is not necessary.
For Windows 10/11: go into %appdata%\Roaming\Games.
There will probably be many folders here with various language names of this title. For English, the folder was sherlock holmes versus arsene lupin
In the appropriate folder for your language should be a setup.ini file with a recent modification date. If so, open it.
Under the [camera] section near the top should be
invert_camera = NO
Change the NO to a YES and save, launch Sherlock Holmes: Nemesis and the mouse Y axis should now be inverted in first-person.
Hope this works, and possibly for other Sherlock Holmes titles by Frogwares.
Post edited September 01, 2022 by MrKevvy