I have found a few mentions around here to problems with the Sly Cyrdel bounty quest. In my case, on defeating Sly I was presented with the option of imprisoning him which I mercifully agreed to. This did not lead to a resolution of the quest, so I traipsed down to the dungeon and met my prisoner with swords and spells and mashed him mercilessly. Still no head and no resolution. I suspect I ought to have sneaked his head off to begin with but am now at a loss as to how to proceed.
Any suggestions, or is this now a dead quest?