Andor's Trail

I'm also a little confused with the quest. I was in the prison and fought the former warden. the questlog now tells me to return to the guard now. But if I approach the Flagstone Sentry, I can just ask him to tell me the story again.
Is there a bug or another NPC I'm supposed to speak with?

/edit: solved the problem myself. I was supposed to first go down, then up. not the other way around.