Andor's Trail

My quest log says,
"I met a guard on sentry duty..."
"I found the former warden of Flagstone prison. I should return to the guard now."

However, there is no option to complete the quest when I speak to the guard. I'm sure I'm missing something, but I don't know what. I received a necklace from the former warden. What else do I have to do ?

There's no option to return the necklace. I've tried.

Ah yes, it's working fine now. Thanks a lot!

But then, the quest log shouldn't say that one must return to the guard.