As soon as we get out of there, we speed towards Solitude. According to Serana's directions, her family's castle should be North West of there on an island not far from the coast. The ride towards Solitude is uneventful, but night is falling when we get there. I'd rather not spend to much time with this woman, but there is nothing for it but to go to the Winking Skeever for a nights rest.
In the morning, while rummaging through our luggage, I remember I had to deliver a book to Adonato in the Bards College. Even before we're properly through the door, they ask us if we want to assist them in obtaining a lost book about some King or other. Not paying much attention, I agree. I mean, how hard is it to get a book? Especially since there probably is a reward in it for us.
This chore being done, we head out. It took us some finding but eventually we find a jetty where we can use a boat to get across.

Unfortunately, the trip across freezes us to the bones. So of course, the doorman gives us some grief before letting us in. Even more awesome is that apparently these vampires are immune to cold or something as there doesn't seem to be a fire going in their hall. So half dead of hypothermia, we face them. This isn't going to go well, probably.
Luckily though, the Lord of the castle and Serana's father is pleased with us for returning his daughter (although, it doesn't seem like it's a warm welcome she's getting) and so he offers us to become one of their kind. Of course, we flat out refuse, but we are in no shape to fight. Fortunately there is no need to, because upon refusing him he teleports us back out of the castle, forbidding us to return. Serana obviously stays behind with her father, something I do not regret.

Best to go tell of this news to Isran, all the way on the other side of Skyrim...
Upon consulting the map, it appears that we can make our way South East past Dead Man's Respite where the Verse of King Olaf should be. Once there, we have to fight some Draugr, but there's not a lot of them and the boys have no trouble dispatching them. What is troubling though, is that there seems to be a ghost wandering in these corridors. It doesn't seem hostile though, it's almost like it's trying to guide us somewhere. And as there is only one route in the dungeon, we don't have much choice but to follow it.

Finally, we come to it's resting place, where we also find the book. I'd have thought it would disappear when we find it's corpse and speak a few prayers over it, but it seems to want to lead us somewhere else now.