From from the back cover:
The ancient dwarven kingdom of wonder and fable is no more! Only the tales of it's grandeur remain to entertain the children, or so you thought.
Then you met Nimron. Distraught and desperate, you alone can pass the gates sealed so long ago. Within are the lairs of bandits, cutthroats, and worse. The evil that destroyed the dwarven home - the Halls of Paradise - is awakened again. Into this horror ventured the dwarven princess Grona Marblefist to reclaim her kingdom. She, like so many others, has not returned.
Now, you must face this peril alone.
Thunderdelve Mountain is a solitaire adventure for the DUNGEONS & DRAGONS Expert game. Players who don't wish to face the fallen Halls of Paradise alone may also use this adventure for group play.