I don't work late, my job is designed so I never have to work late. However, I am occasionally in the office alone. I usually just lock the door when I'm here by myself, we have next to no office visitors since we are a trade company. I now knock wood, but when I leave it's full daylight. There is a car repair company across the street (ironically) that's always open when I go and we know those guys. So I'm good that way!