When i was a fresher at university i moved into this block of flats which used to be a prison but had been renovated and converted into student accommodation. the place had been nicely done up, 7 bedrooms. There were only 5 of us so two of the bedrooms were not in use. my flatmate came into my room late one night all panicky. she'd left her room to use the bathroom and with the corridor light switched off noticed a light coming from under the door of one of the unoccupied bedrooms. my other flatmates had gone home for the weekend so it didn't make sense for the light to be on. we decided to check it out. we walked up to the door and tried the handle. it was locked, as it always is. i tried it again just to make sure...definitely locked. so we stood around contemplating the fact that maybe the light had always been on and we'd just never noticed. i didn't realise i had been leaning on the door until it started opening. we were both soo freaked out we immediately ran out of the flat and called security. but whoever or whatever was in that room had left by the time security came. the only thing in the room was a pair of my flatmates flip-flops she had lost a few weeks ago. we had the locks changed the morning after.