A Reddit user was left baffled when he rewatched motion camera footage to find something sinister apparently moving inside his house after he left for work.
User "blin11" said his flatmate heard sounds of a door opening and shutting when he was getting ready for work in the morning.
Determined to find out what made the sounds, he installed a motion camera in the living room to capture if anyone was trying to break into their apartment.
He said he received a "motion detected" notification at around 11am, when he was certain no one was at home at that time.
In the video, his bedroom door is indeed seen opening and closing on its own.
Everything else remains untouched and no shadows or reflections can be seen walking past in the clip.
The user explained: "I got home from work and checked out the door. It was fully shut like I left it this morning.
"I don’t see anything else out of place, and no extra fans or anything were left on by my roommate.
"I’m getting a static cam set up for the other side of the door, and I’m going to talk to my roommate about it when he is back from vacation."
Some viewers were certain it was evidence of ghost sightings.
One said: "That for sure is a ghost."
Another added: "It’s a ghost. All these people are just in denial. It is a ghost and you should be aware. If it’s peaceful and nothing goes too crazy, then you should be ok."
Others suggested it could have been caused by a working air conditioner.
"Could it be related to your air conditioning? My house has a door that slams when the air conditioning kicks on if we leave it open. If the latch is weak it might also pull it open," one viewer wrote.
A second thought the same and commented: "I was going to comment that it might be the AC.
"At my parent's house, some doors shut and open whenever the AC turns on and off. Or perhaps a draft from the front door is causing it?"
But the uploader responded to the sceptics by saying the door was actually locked shut.