Amusei is a man trying to join the theives guild. At the first Theives Guild quest "May The Best Theif Win" he says "Thats Not Fair!" and quits. Later he gets caught in Leyawiin and is sent to prison. You can help him escape and get the ring back from Alessia the Countess. Next time you see him he gets caught with another theif and gets locked up again. If you talk to a prisoner there they will talk about A Pale Lady taking people. If you got to the wine cellar and pull a candle a door will open. In there a Vampire is in there and isnamed the Pale Lady. She has the key to Amusei's cell but the other theif is dead.