Speak with Lady Jaina Proudmoore in Theramore.
You must bring news of our findings to Lady Jaina without delay! If the Defias were transporting a prisoner, there's no telling who it might be or if the person is still alive!
One thing is for certain, <name>. The Defias wouldn't go to all this trouble for some petty grudge. Their prisoner must have been someone of importance. Lady Jaina would know better than anyone else what these findings mean. You'll find her at the top of the mage tower at Theramore's center.