A Plausible Theory
One day, as she cleaned the house, Tracy realized that the sounds in the attic were also moving from room to room. Then, it came to mind that the strange noises could very well come from a possum or raccoon that had somehow found his way into the house.
She thought she would need to call animal control. However, it was a Saturday and they did not work on weekends. So she decided to wait until Monday. But the presence in the attic seemed to have other projects.