In the Chasing Echoes quest, I'm at the point where I'm supposed to "Speak to Serana" at the castle. So I meet her there, speak to her, and no matter what I do, after the prliminary greeting and my request to enter the castle's secret entrance, she says: "Well, I don't just take anyone... Get rid of this interloper and you and I can be on our way. I'll wait for you at the dock." My problem is that there is absolutely NO ONE else around. It doesn't matter if I speak to her at Dawnguard, at the Castle, or anywhere in between - she says the same thing. I have tried killing anyone within a half-mile radius - no joy. I've tried dropping everything I own, thinking maybe she's sensing a random soul in my inventory - no luck there either. No matter what I do, I can't get any other dialogue out of her, nor can I move forward with this quest, which is holding up the main quest, as well. Any one else encounter this?