Once returned from killing all the raiders in Town Under Attack, the player will see Ruby distraught in the Carbon Warehouse. A raiders has stolen the locket once belonging to her grandmother. Ruby wants it back and is asking for help. Fight your way through the railyard on your way to the mill, and at a certain point one of the raiders you kill will drop it. After your business is concluded in the mill you can return the necklace to Ruby before telling the Wasteland Stranger you are ready to leave town.