Is missing dialogue (and has been reported in bug fixes by Inquisitor), but I was curious if anyone knows what the quest involves? I received it a couple days ago, and haven't a clue who gave it to me, or what I'm supposed to be doing with it :(
You should simply go to Stannis and tell him about the letter. You will get positive relations with him and gain a few honour points. I think that's all there is to it.
I couldn't remember if that was the quest or not, thank you!