Stuck again in DQ8 (spoilers)

I found out that Dholmagus murdered the owner of the Casino in Baccurat but I don't know where to go now. What do I do now?

If you've already gone into the hotel, and heard the busboy and the bartender talking, and interrogated the bartender downstairs for his info, then you need to get in your boat and go to the island that the waiter told you about, which is in the north. after trying to gain entry to the temple of darkness, you'll have a chat with the guards of the town that are there as well, and they'll clue you into a way to break the curse.

And if you havnt, just go into the hotel during the day, talk to people until you find someone asking you to find the bartender who went upstairs to chat with his friend.