You entered the place of his past horrors and found the poisoned note under the table. Right when you pick it up, you hear a rattling noise at the end of the hallway. You put the note in your inventory as you walk over to the location of the sound but see no one. It’s probably just the wind. I mean, the building is very old. Never mind that, there’s a book on the table where the sound was coming from. You read it.