The Flooded Barrows of Han'Mei

The party awakens in a dimly lit room smelling of mildew and ash to a lone dwarf in dusty chainmail tending their wounds. They learn that a freak storm on the surface decimated the town above and that they were accidentally placed among the bodies sent down to be hastily cremated. Instead the dwarf before them figured they were still alive and tended to them until the barrow started flooding and communication was lost with the surface. Rescue is unlikely for a long time, and supplies are low-- the party must escape from the barrows by scavenging for food and water while dealing with whatever enemies that may be found lurking in the dark.