The deepest shaft in Saltmere broke through into a city that was sealed on purpose.
Saltmere lives on the salt it cuts from the mountain, and for two hundred years the mine has only gone down. Three days ago the deep shaft broke through into a street: paved, lamplit by something that still glows, and lined with doors carved shut from the outside. The mining company wants it surveyed and stripped before the crown hears of it, the temple wants it sealed again, and something down there has started moving the miners' tools in the night. The foreman, the surveyor, the priest and the smuggler are the only four people who have been past the breach and come back up.
4 roles. You take one; your friends take the rest, and the narrator plays any left over. Anyone can bring a character of their own into a role instead.
A third-generation foreman who knows every timber in the mine and is responsible for the men who went down the new shaft.
A company surveyor sent from the capital to map the breach, who is beginning to think the map is being drawn back.
The mountain temple's keeper of old records, sent down to bless the breach and secretly ordered to seal it again.
A salt smuggler who has been using the old drainage tunnels for years and was in the city before anyone blew a hole in it.