Well you're where you should be all the time, and when you're not you're with someone who was killing the wife of a postman.

The story:

I was on a roadtrip with some friends, and this was on a cd that we were listening to, and we all sang along very enthusiastically, until it came to these lines when we all mumbled, and I offered up my interpretation of the lines, everyone laughed at me, and when I got to a computer I looked up the right lines.