Bring the Sealed Description of Thredd's Visitor to Master Mathias Shaw in Stormwind.
I really haven't a clue, [player]. There is someone else who might be able to help you, and it so happens that he owes me a favor for--well, let's not get into that. Master Mathias Shaw of SI:7 can be found in the barracks in Old Town. Shaw has his thumb on most of the shady, or underhanded dealings of the city.
If anyone knows, it'd be him.