The girl

 The girl grew up healthy and happy, making frequent visits to her grandmother, who seemed to have no further problems. Years later, as the girl prepared to leave for college, her grandmother made her a gift. It was a sewing box, crafted from wood, with intricate designs on the sides. When the girl opened the box, she discovered a skeleton key lying atop a thick piece of paper. On the paper was a note from her grandmother, written in a shaky scrawl.

'My dear granddaughter, from time to time you will hear stories of horror that take place within the walls of this apartment. I want you to know that these stories are true, and to use this key to protect yourself from whatever dark force lurks in the shadows of this place. I'm sorry not to have been able to reveal it to you sooner, but I promise you that you will be safe now.'

The girl went to college and forgot all about the strange note, but when she returned home, she found that it had haunted her dreams. She kept the key to herself, not sure what it meant, but something inside her warned her not to forget it.

The girl continued to visit her grandmother, who grew ever more distant and elderly. One evening, she asked the girl to go to the bathroom and turn on the lights before she went to bed. Strangely, a chill ran through the girl that made her hesitate before she agreed.

When the girl got to the bathroom, she noticed a faint glimmer in the corner of the wall. She stepped closer and realized it was coming from an old lock, with the keyhole shaped like a small bony hand. She immediately recognized the key her grandmother had given her, and knew that this was the dark force her grandmother had told her about.

Shaking with fear, the girl opened the door and stepped inside, discovering a long and narrow hallway. Lights flickered, and the walls seemed to be made of bones. Feeling her way along, she soon found the exit at the end of the hallway. From there, the girl was safe.

The next morning, when the girl told her grandmother about the strange hallway, the old woman smiled and said that she had been waiting for this moment. She then revealed that she was the dark force, created eons ago by a powerful witch, cursed to remain in the walls of her own home. The witch had placed her bony hand into the lock to keep her from escaping.

The little girl had unknowingly broken the curse and set her grandmother free. The old woman lived out her last few years in peace, surrounded by family, before passing away.

The girl never forgot the lesson her grandmother taught her, and found courage in the darkness that surrounded her. After all, it was only in the deepest shadows that the light of a new dawn could be found.