A teenager filmed a Musical.ly video while home alone. Except she wasn't 'alone' at all.

It’s the creepy internet mystery that makes us want to put down our phones and look over our shoulders AT ALL TIMES.

Imagine this – you’re a teen at home alone, playing around on Musical.ly, and it turns out you might not be as ‘alone’ as you thought.

This is apparently what happened to YouTuber MrBunnyFingers‘ friend’s cousin. (What a mouthful.)

In the video the teen is making a Musical.ly clip when something moves across the top right-hand of the screen, just above her shoulder.

Did you catch it? Watch it again. It’s right at the start of the video.

Is it a person? Is it a demon? Is it Superman? We don't know. It almost looks like a human running past wearing a balaclava.

MrBunnyFingers claims that her friend's cousin was home alone at the time and the only pet they have is a cat.

Because the internet is a crazy lil' machine, the video was promptly posted to Reddit, and the conspiracy theorists have come out to play:

What do you think it is? WE NEED ANSWERS.