I'm going to have to wait for that walkthrough cause I looked all over the celing in the main room and the elevator room and there is nothing there and the coffin room has no way to make the light brighter as far as I can tell.
Same here, completely out of ideas.
HINT doesn't help at all, the partner just brings up the fern (I've already taken the fern trimming).
Or the books (already checked all of them).
Or the stairs, the desk... (already, already, already...)
Honestly, the partner system has been so spectacularily unhelpful this whole time - anything I ask about, they'll always
respond to with outright hostility. Like...
<enters name of inventory item>
PARTNER: wanna try making sense? you worm? you utter baffoon? what???
<enters name of other object in the room>
PARTNER: i will actually murder you. you're insane. stop.
<enters words relating to the characters>
PARTNER: i have never heard of "police". perish
For anyone still stuck (SPOILERS):
That metal fragment is in the cave after all. It has nothing to do with light in-game as far as I can tell. The guide text file says it's hanging from the ceiling there, but I still had trouble finding it. It turns out it's at the end of one of the hanging chains. Because it's metal and rounded, it looks like part of the chain, so it's really easy to miss. You have to look closely to see it. If you hover the mouse over it, it will change to a yellow hand cursor.