The other day I was leaving my apartment and I ran into a man coming up the stairs. He was about 30, slightly balding with a short beard. I know everyone in the building but I knew he didn't live in one of the other units.
We made eye contact. I knew I knew him but I just couldn't put my finger on it.... and then I realized who it was....

Of course I knew him!

fast forward to tonight. I'm walking up the west slope of Nob Hill on California. A man approaches me. When we got close enough suddenly I realized I knew this man... again, I couldn't quite place it. Same guy, but tonight it took me even longer to figure it out.

My housemate.

I see him so rarely that I don't even know who he is when I see him on the street. He's been here for about four months and I don't think I've had a real conversation with him in at least two.