[MENTION=6702445]jayoungr[/MENTION]: That's all right. When the PCs returned from their initial foray to Lance Rock, I had a tremor shake the town while everyone was in the Helm having dinner. The town elders insisted everyone remain calm and then dashed outside and headed for Waelvur's (with the intention of going to the tomb to ask Larrakh what was going on). The PCs were immediately suspicious and followed, so the elders didn't make it any further than the wagonworks. Elak Dornen told the PCs in no uncertain terms that they weren't wanted and that, for the greater good, the PCs let the elders do their jobs undisturbed.
The PCs backed out when Waelvur's wainwrights brandished their tools menacingly and decided to go have a snoop around Dornen's quarry and office. They found nothing out of the ordinary, of course. Then they remembered about the other quarry and went and knocked on Mellikho's door. I had Albaeri growl at them for disturbing her after hours and asked them to come back in the morning ... but instead, she found them and told them about the rumored treasure in Tricklerock Cave. Despite the players smelling a trap, they sent their PCs off to the cave anyway ... and, of course, there was nothing there but some stirges (and a hungry ghoul that was all that remained of the previous adventuring party to have gone into the cave).
I think that's set things up enough. So I'm going to make it so there's another tremor followed by the sinkhole opening up just as the PCs are returning to town.
By the way, speaking of the sinkhole ... I superimposed the Tomb of Moving Stones and Red Larch maps in Photoshop. Putting them at the same scale, I found that by rotating the tomb map nearly 180 degrees, I could get the secret passage from the tomb to lead to the quarry, while the secret passage from the cave led to Waelvur's ... and that put the sinkhole in the middle of the intersection in the upper right corner of the town where the Larch Path starts.
If you try to use the two maps as drawn up, you end up with the passage from the cave leading to the quarry and the secret passage from the tomb leading to Waelvur's (the opposite of what the adventure says), and the sinkhole ends up being in the open land to the west of town.