Mission 6: Return to the Tower
Bone Charm 6-1
When you first start the mission, swim into the water locks and climb up the pipes. Before going any farther, look up on the left side to see and open window. Blink up and then across to the catwalk on the opposite side. Blink across to another set of open windows and find the bone charm there beside a corpse.
Bone Charm 6-2
Once you enter the tower and make your way to the second floor, there is a fireplace in the corner of the corridors. Use the light to the right of the fireplace and it will open a panel at the rear. Go inside the fire place and grab the charm on top of the shelf.