Bring a Lieutenant's Insignia to Thrall in Orgrimmar.
One thing I will not tolerate are traitors in our midst, [player]. But I would be a fool to play my hand so early--it would not sufficiently cut the corruption out of our lands and only cause the infection to grow worse.
But you, a young adventurer, could go places my agents could not... could learn the truth... could find the true head of the beast.
If you are brave enough, then enter Skull Rock to the east of Orgrimmar, find a lieutenant's insignia off one of the Burning Blade there, and return to me.