As you sit in the kitchen, diligently working on your homework, the sound of your brother and his best friend yelling at the TV fills the house as they play video games. Suddenly, your brother's phone rings. It's a call from his job, and after a brief conversation, he grabs his things and leaves in a hurry. You return your focus to your homework, the house quieter now except for the hum of the TV in the background. But then, a strange sensation washes over you — the unsettling feeling that someone is standing right behind you.