It is strange that the pendant Marg stole was in the hands of common soldiers. Perhaps its owner was in disguise, or perhaps the soldiers themselves stole it!
Regardless of which is true, this is a noble's pendant and we must discover its true owner if we are to unravel its mystery.
Take the pendant to Zor Lonetree in Orgrimmar. He is well schooled in Alliance politics, and will know if this pendant has a history among the nobles of Stormwind.
