Whilst travelling his usual route one day, your character encounters an invisible barrier that he can’t cross. It doesn’t seem to affect or even be noticed by anybody else. When he investigates, he finds that the barrier is circular; it’s not keeping him out of anywhere, it’s keeping him in.
Questions and ideas for follow-up:
- Where is the centre of the circle? Is it centred on his home? A church? The spaceport? An allegedly haunted house? Or somewhere that seems totally ordinary?
- What happens if he tries to cross the barrier in a vehicle such as a car or train? Does the vehicle’s engine fail? Does the vehicle go through and just leave him on the ground?
- What happens to the barrier if you go up? Is it a hemisphere, or a cylinder? Or perhaps it’s a tube leading somewhere.
- Why is the barrier there, and why him? Possibilities include: an experiment with him as a test subject; he’s actually an alien/fallen angel/demon fugitive and the authorities are catching up with him; a research project gone wrong when he was exposed to a chemical; a curse; or maybe he asked for the barrier because he knows he can’t be trusted.
- Is there any way to destroy or disable the barrier? Are there other people around the world having the same problem with barriers of their own?
- What happens if the barrier now starts slowly contracting, leaving him with less and less space every day? Will he discover he’s not the only person trapped by ‘his’ barrier? What happens when the barrier gets so small he can’t move at all? Then smaller still…