A little background on the stories I am going to tell.

I studied in Maris Stella High School, which is located on Mt Vernon.
Mt Vernon used to be a cemetery and the graves on the Hill were never fully exhumed based on what we learned of the school history. So the school was finally built over them.

It was the Secondary One Orientation camp. After dinner, all the sec one students, including me went to the hall to listen to our discipline master talking about the history of the school, how it was founded etc.

Slides were shown using the OHP on the main projector screen. As the talk goes on, suddenly the screen rolls up. The discipline master was unhappy and shouted to the rear of the stage to tell the AV boys to roll down the screen and stop playing. A few shouts but no replies. The discipline master then ask one of the student councilor to go look for the AV boys and they were all outside the hall.

Probably the discipline master sensed something bad, he and 2 AV boys went back to the back to find the switch. It seems that that no one was at the backstage, there were only 1 back door but it was locked and no one went in and out. There ere a few noises after the trio went in and finally the projector screen came down again. The trio came out of backstage but the discipline master looked perplexed by the issue. The history of the school was then quickly rushed through and we were sent packing back to our tents.

The screen was used before and after the incident and never had an issue but it was only used during daytime. That night was the only time it was being used at night.