The plot is simple: An old mine which was abandoned because the miners reached an ancient tomb. It has been closed for so long that most have forgotten why it was abandoned in the first place. An NPC has ventured to the mine, possibly to see if it still contains ore, and has disappeared. The players are then hired to go there and figure out what happened.
An abandoned mine entrance at the foot of a cliff with a corpse outside, having obviously dragged themselves out of the mine before bleeding out.
The first floor is a small area once used to store supplies. It has recently suffered a cave-in which the players must get through. Beyond the rubble is a large room with holes in the walls. This is an ideal area to encounter some insects, possibly beetles? They can dart into any of the tiny holes and emerge somewhere else, leaving the players constantly surrounded. In the upper part of the room is the ladder down to the mine.
This is the actual mine, a sprawling complex of twisted tunnels. An underground river winds through the complex, far to deep and rapid to even contemplate crossing. The blood trail has obviously crossed a now-collapsed rope bridge, so the players must find a way to fix it. In the upper-left is a wench with a hook on the end, perfect for launching a rope across the chasm. In the lower right is a rolled up and unused rope bridge, which they can then use to replace the old one with. Fill this mine with whatever you see fit, preferably something which might come out of the mysterious tomb in the upper-right (Undead? Demons?), which the players can access once they've fixed the bridge.
I've not mapped an actual tomb, because you're free to pop in any dungeon you see fit. Hope you guys enjoy these maps!
Also, I have versions of the maps without the corpse, blood trail, fixed bridges and without any sort of furnishings (Crates, etc.), so if anyone needs that, just ask.