Quest 'Get Junior': Where do I find the documents?
Go to your quests and do the find the secret stash using witcher sense. When you get to the spot use witcher sense and turn the torch to open the wall. You can then loot the place to get a letter and that will complete that part of the quest.
It's in the arena where you beat up minor men with the dwarves. It's all the way back around the arena next to the chair.