Play@YSDC

First Aid 30%: 1d100

1d6/2

"You know, maybe I should have taken up all that doctoring stuff. How hard can it be?"
In what can only be called a miracle, Jerry manages to dress some of William's scrapes with some leftover rags.
"If you aren't so keen on waiting, we could go back from here and check if there's anyone behind us."

"Thanks," says William. "Going back would mean climbing back up the rope. Plus, we know there's someone behind us, someone with a gun. If we climbed back up, we'd also have to climb back down afterwards and probably get hurt again. The woman who needs help is ahead of us."

Jerry looks up at the top of the ledge, and looks back down at William. He didn't care much for climbing, and if there was one thing he cared for less than climbing, it was falling.
"You know what? I think you should have brought a ladder. Let's press on, and once we find that woman, we can sort out the man with the gun."

That’s 2 HP recovered for each of you.

Moving down the tunnel for another 50 feet or so, Jerry and William entered into a wider tunnel than ran perpendicular to their own. To the right the light of their head torches illuminated some old, long abandoned workings but to their left, this new tunnel stretched away into the darkness, with fresh tunnels going off to both sides.

From somewhere in front of them a low moan, like the wind, could be heard.

William examines the ground for any traces of recent passage.

William couldn’t be sure but was that a scuff mark on the floor, like something - or someone - had been dragged through a patch of loam on the floor?

"Winscott must have been brought down here, but by what? I'd think that if an animal bit him and dragged him down here, there'd be a trail of blood. If it was a person, they would have left a rope behind on that ledge unless they have some other way out." Jerry observes, moving forward to try and figure out the strange sound's source. Could that hapless travel writer have stumbled into some kind of criminal operation and gotten himself kidnapped? Jerry had heard of the use of tunnels for smuggling before, but nothing quite as extensive and downright bizarre as these caves!

"It might have been his wife down here," replies William. "That would explain the woman's cry we heard earlier. Whatever the case, it's that way." He points out the scuff mark.

Moving down through the space, Jerry and William could see an opening to their right. The light from their head-torches lit the carved surround of the opening, which showed carvings of serpents and geometric shapes. It was from this opening that the low moaning sound emerged.

I think I’ve mentioned this before, but Winscott didn’t have a wife. The only woman associated with the property was his late great-aunt.She’s dead so probably isn’t make much noise… probably… …

William shines his light into the opening and keeps his shotgun ready.

The spoiler button's contents aren't showing because there's an apostrophe in the text that's supposed to be displayed on the button, but I was able to see the contents (which may have apostrophes) by quoting your post.

The opening lead to a short passage that opened into wide grotto beyond. There was none of the phosphorescing lichen in here but crystal deposits on the walls glittered in their lights. The ceiling was high up above their heads but their attention was drawn to a bizarre twisted structure spread across the far wall.

It was fashioned from interlaced bronze pipes and studded with crystals of various sizes and colors. The pipes pierced the wall in numerous places while the other ends ultimately end in spikes. There was a rock formation 20 feet in front of it, carved into a sort of seat, although it didn’t look like it was designed for a human to sit upon.

The low moaning continued…

"Who the hell could have built this? This wasn't the work of any cave-man, that's for sure!" Jerry whispers much louder than he probably should, approaching the bizarre object to get a better look at it. What purpose could something like this serve?

William directs his light - and his shotgun - in the direction of the moaning.

Drawing closer, Jerry and William could start to see the structure in more detail. A score of human heads were perched upon the spikes. As they reached the chair, they realised that the sound they had been hearing was coming from the heads, which moaned softly in an ululating chorus.

The heads had been preserved with sinuous runes carved into their leathery flesh. Their eyelids were closed, but their mouths and the muscles of their throats moved as they sang! Some of the heads belonged to men of European descent, while others belonged to men and women of African descent. The whispering song that issued from the heads had a sort of ethereal beauty, but the overall spectacle was enough to send the two men reeling…

SAN check (1/1d4) and Listen, please.

William gapes in shock. He has ears only for the bizarre singing.

Sanity roll (current level 52) for the singing heads:
d%
Sanity loss:
1d4
Listen roll (68% skill) in the grotto:
d%

Sanity 55%: 1d100
Sanity Loss 1d4: 1d4
Listen 25%: 1d100

Jerry, utterly disturbed by the living faces, briefly and wordlessly excuses himself from the room to try and come to,terms with what he has just seen. Whatever Lawrence was involved in, it was real. His brief period of thought, however, is interrupted as he notices a sound...

As William stood looking aghast at the hideous structure, Jerry retreated into the short tunnel from when they came. From behind him, there was a scampering noise, like some beasts running through the caverns…

William hastily follows Jerry.