Enter the mansion through the back door; if you haven’t been here yet, you’ll have to disable the traps in front of it. You’ll see the glowing keyhole in the foyer, but first you’ll have to get around some traps. The trap by the wide stairs can’t be disabled, but you can push and pull the statue onto it to disarm it. Use the key and enter the library. Loot both chests for some treasure and the letter you need, and report back to Jean Luc. He wants you to take the papers to Estelle Fouchier to have them translated, so go talk to her. She’ll quickly do the translating and send you back to Jean Luc. Talk to him for a nice reward and you’ll complete the quest.