After deciphering Eveli's letter, you can speak to Mulzah at the Greedy Gut. After saying the secret words "Orcs Don't Smell", she will give you directions to the secret room past the storage area.
Orsinium Guards have temporarily closed down The Greedy Gut, and have refused to give Mulzah any detailed information about why. Mulzah can be asked for ideas on how to sneak inside.
One of the invitations King Bazrag has sent out must be delivered to Mulzah, who will remark that she is merely an innkeeper's daughter. She will later be at the Castle Overlook during the funeral, and later inside Scarp Keep.
When Mulzah is first met:
Welcome, welcome. You've discovered the Greedy Gut, the finest inn and tavern in all Orsinium.
But if you're looking for a really good tome, I'd visit the exclusive cornerclub in the Residendal District if I were you.
After repeated conversation:
Have you visited the new museum? I'm not much into history, but I understand the place is pretty good if you happen to be interested in that sort of thing.
Me? Old stuff kind of gives me the creeps, so I avoid the place like the plague.