theres 1 outside number 2 as well. go to the right. its the map marker that looks like a shield crest. I believe number 2 is where all the afflicted r right?
Is "Lost to the Ages" a quest that can only be done by staying with the Dawnguard?
You have to read a book called the Aetherium Wars. It is on a bookshelf in the dawnguard castle. I do believe there are others around, but that is where I found it.