Fishing a Naked Man Out of a Well

The group chose to start at a dungeon. I took the bones of a popular small dungeon, ripped it apart and molded it to fit Dolmenwood. I placed it near the Woodcutters' Encampment and we were good to go.
They found their way inside through an old oak and almost immediately heard someone calling for help from a well in the first room. The man in the well turned out to be a Drune called Andramath. The water had dissolved everything he owned.
The players weren't sure whether they could trust him, or whether the water was safe. What convinced them to help was the bargain he offered. He had gone down looking for some stone tablets he believed were inside a coffer at the bottom of the well. If they helped him out, they could have whatever else was inside. Andramath himself hadn't dared open it while still standing in water that dissolved almost everything.
Tom volunteered to get naked and climb into the well to pull Andramath out along with the coffer. They got some gemstones, Andramath got the tablets he wanted, and Crispin, one of the few people in the party who could actually write Woldish, copied their translation onto the wall in chalk. The players arranged to meet him again at the old oak in six days.
The session ended when Curlip saw a passage full of cobwebs and promptly set it on fire. The fire startled a big black spider lurking on the ceiling, which panicked and retreated deeper into the barrow. A talking skeleton fell out of one of the spider's bundles and scattered itself across the floor while cursing its situation.
I judged from the reaction roll that the spider would rather flee than stay and fight. I like that as a small change to the dungeon state. There's now a large spider somewhere else in the barrow.
I was surprised by how careful the group was about entering the dungeon. I also don't think I described the area outside particularly well. There was a knocked-over cairn that I never actually called a cairn, so the fact that nobody investigated it further is hardly surprising.
There wasn't much room for proper character introductions at the table either. With five players and only an hour I chose getting into play over spending much of the session on introductions, which I think was right. Still, I don't want "we only have an hour" to become an excuse for ignoring the characters completely.
I'm less happy with the starting hook, which I took straight from the rules and didn't dwell on because I wanted to get playing. In retrospect this was probably the one time I could have afforded a more deliberate hook. Once the campaign is running I want those directions to emerge from play, but at the very start there isn't any play for them to emerge from yet.
But let's see how it goes. I have a feeling they're pretty good at finding their own goals, so it might not be an issue at all.