Turns out I needed to visit the cave first to get the key to Candace's room, but in order to do that I had to look at the cave, ask the housekeeper about it, and go back to the cave. The poster and the whisky are both in Candace's room.Hmm.. Sorry, it's just been too long since I played to help, then, if those clues don't help. Maybe you could load an older save (right after arrival) and see the poster in the bedroom? You only have to discover the name of one town, IIRC. It may be that you can't find the whisky until you discover that the victim had been drinking before she died.
I hope someone who has played more recently can help you more than I could.