Time to get out of here with minimal fuss. There is a Level 2 Locked chest nearby the chest that had the Golden Key. There is also an Initiate Chest nearby the with the Raider Outfit.
Head out to the West and down the stairs. Continue downward to the second landing. Head over to the Western end of it and have Arno leap for the wooden beam sticking out of the wall. Use it to swing over to the next landing. Run to the Southwest over to the ladder and climb up it.
Head over to the Northeast from there. Use the cart to get the height to reach the wooden beam in that direction. After that, follow the path to the right and start going upwards. Just run through the next room and don't stop. It will get some attention, but they won't be able to stop you or hit you. Just keep moving to the Northeast to find your original point of entry. Just make it up and out of there then become anonymous.