So i am playing the dawnguard dlc and I have run into a problem. On the Chasing Echoes quest, after I leave the castle to meet with Serana at the doc, I tell her lets go look for your mother, and she says that she doesn't take just anyone, get rid of this interloper and then we will talk. I have nobody following me except for Shadowmere and I have tried killing him and that has done nothing. I am really stumped and have resorted to playing Oblivion because I cannot advance anymore in Skyrim. If anyone has any ideas or suggestions please help!