Gave it to the thief. Denied her at first, thinking "She's probably gonna steal it. Do I trust her with something so valuable?" But the next time I had a thought: "She does offer to... well... steal for me, so maybe she'll be loyal." And I hired her. The only other guy was a short knight (I don't know if he was the right guy to hire) and I had denied him. I just wanted to kill the dragon and see what happens so.