When I was nineteen, I shared an apartment with a friend (Lori) that I worked with. The apartment was in the same building that my grandfather had lived in prior to his death.
One day Lori and I got up early and decided to head into the city for the afternoon. Before leaving, we tidied up the kitchen, made sure the doors and windows were locked etc. - normal stuff. The apartment was on the ground floor, so we always made sure that the sliding door was locked and secure (by placing a log stick in the track so that even if the door was unlocked, it would not be possible to open it from the outside.
I remember when we left, surveying the kitchen and taking pride in the fact that we had such a nice tidy place - no dirty dishes lying around etc.
Well, about ten hours later, upon our return, we entered the apartment. Something didn't seem right, but I couldn't put my finger on it right away. However, upon entering the kitchen, I noticed two mugs sitting on the counter. Strange, I could have sworn the counter was spotless when we'd left. So I went over to the mugs and put my hands on them - they were hot!!! I then put my hand on the tea kettle - cold as ice. No tea bags anywhere in the house, no tea spoon, nothing.
We were completely spooked by this, as there was no possible way anyone could have gotten into the apartment - the landlord didn't even have an extra set of keys to the place, and the only thing I could attribute it to was that grampa had been there and made tea for us!