After obtaining the final case file, the "Murder Axe" quest has a follow-up, but it takes place in a later map. You can also interact with the nearby wall to collect some dust.
Let's interact with the wall now to slide down.
After sliding down, you can see a corpse by the cliff edge. Interacting with the corpse grants you the book [Orthodox Alliance Miscellany #1: Record of Injuries and Illnesses of Orthodox Disciples].
