Treasure trails clue scroll
For the clue scroll: Go to the village being attacked by trolls, and search the drawers in one of the houses.
Go to Dunstan's house in Burthorpe and search the drawers: "Wait till I get my hands on Penda, he's nicked the key again."
Go back to Dunstan's house and open the drawer with the key in inventory. The key disappears and you will obtain another clue scroll or a reward.