You got an odd text from an unknown number. It read:

I'm in your walls.

Despite how strange and creepy it sounded, you assumed it was one of your friends pulling a prank on you, and promptly blocked the number. Now, a week later, you've started to hear shuffling, coming from somewhere in the walls. You've checked everywhere, but found nothing. Sitting on a chair near the wall, you heard some tapping. There was a soft voice.

Psst... I told you I'd be in your walls...