Hidden Treasure
Quenton quickly directs you to a trapdoor in his house. He also gives you the key the place.
Go into the trapdoor beside Quenton's bed.
Open the door with the key Quenton gave you.
At this crossing, you will find a bunch of thieves looking for something. Say hello to them with fire and poison or whatever you have on you.
The left exit leads you into the Bastille. But there is no need to go there so head to the right exit. The key to open this door can be found on the floor. Take it and open the door. Climb up the ladder.
When you exit, you can immediately see the white ember just sitting there in a ruined shack.
Take the white ember to complete this part of the quest.