I made some research and this is how it looks like: you must clear this site during the prologue. If you are still in the prologue, you are likely to encounter 3 ghouls there. Once you kill them and meditate, a 4th one will appear. Once you rescue the site, there will be people praying and a herbalist NPC. Now, when you have already finished the prologue, if you return there, the site will be empty (no people, not NPC, no monsters). If you did not clear it during the prologue, it will be empty too, with no way to clear it.
So currently the only solution is to make sure to clear it during the prologue.