Although I've played through several times, this time I can't start the quest from Sir Dante to steal Sir Patrick's deed. AFAIK it's the only way to access the Assassin's guild. There is a pair of boots there that, best I remember, are as good or better than the vampire boots.
I spoke to Randell and got the request to bring back the brooch for Sir Dante's wife. I got the brooch and gave it to Randell. He was pleased, gave me some money, and said Sir Dante should be glad to speak with me. I had saved before delivering the brooch, so when speaking to Sir Dante, I was able to try every possible path in the conversation tree. Nothing worked. Although he made it clear that he didn't like Sir Patrick, there was never an option for me to help him in any way. I tried exiting the game, reloading, and trying again without success. Any suggestions would be appreciated.