You hear an odd noise. You imagine what it is. You notice everything looks different. Everything is too quiet. Your subconscious conjures up thoughts of monsters, ghosts, robbers, killer clowns, evil cleaning ladies...

I've been at a restaurant late at night doing deep cleaning 4am before and there was a food truck delivery, they drop it off and lock up, I didn't hear them because I had my Bluetooth in and he scared the living Christ out of me.