[Gem Mountain - North]

((Oh, right. I forgot to say. If you ever don't like the direction something's going, or you think it's a touch too far, or you want something specific, just say so and I can change what's going to happen.))

Of course there's a few scrapes on the floor on the west side of the room, suggesting a hidden passage behind a bookcase. They're near where the scrapes from the chair and desk are, so the bookcase's floor-scrapes are a little more camouflaged than such hidden passages usually are. What sort of self-respecting castle doesn't have a few hidden pathways?
Unfortunately, none of the obvious books seem to trigger the passageway, which suggests there's some other mechanism that would open it.
Also, unfortunately, it seems Rein doesn't have the time to do that, because of Tina.

And the corpses.

With their lights shining directly on them (and having approached them more), they can now see more details about them. The bodies have burn-marks. Not just anywhere, though - the burn-marks are especially concentrated around the mouth and nose and - on the few that have small cuts or wounds - there's also wounds there.

Of course they don't move while Rein kneels by them. They're corpses. Corpses don't move. But...judging by the the way the dust on the floor is, around them, they obviously weren't dragged. As one might expect from zombies, the dust-patterns seem to suggest they walked there (more recently than the construction workers were here, but still months ago) (but their clothing suggests they are construction workers, which means Rein is right to be worried that they're undead) and then collapsed.

Careful examination will reveal three important clues as to what happened.
First, besides the burns, there's no other obvious injuries on them that would scream 'this is how they died'.
Second, in addition to the burns around the mouth, etc, a close examination reveals that there's also burns inside their mouths.
Third, the bodies are significantly warmer than one would expect for something sitting in a cold cave for years.

Fourth, because you need to go partway down the hallway to reach them, they can now see farther down the hallway past the turn. The rest of the hallway is lined with torches, but the torches farther down the hallway are even dimmer. And, one by one, the flames on those torches go out.

In fact, in the entire hallway, all the torches are slowly dimming. It's slow enough that it's hard to notice until suddenly you'll realize that nearly all the light in the hallway now comes from the flashlights, and maybe the ray-gun depending on how brightly it glows. When I imagine a ray-gun, I usually imagine it glowing.