Ghost?

Maybe I do believe in ghosts after-all. A sudden turn and glance out the window at work and I thought that I caught a fading glimpse of two legs walking by. A more focused second look produced nothing. Whatever it was had vanished around a corner into that middle ground between afternoon and evening. Now that I'm distanced from the moment it's easy to call it a shadow or maybe visual lag from my bifocals but it did seem real at the time.