They took 'im to the tower down the way, and it looks like you'll have to fight the whole surly lot of them if you want to free him.
Use the Pilot's Log in your inventory to look for clues.
In Progress Edit
Cleave those thick skulls of theirs and rescue that Dwarf!
On Completion Edit
It ends with an ominous note that he can hear the approach of greenskins.
- - Upon Examination: Pilot's Log