Feels like the 'is it smiling' part kinda ruined the atmosphere a bit. Also, when someone runs past the window, we assume there really was someone out there, but in the end it seems there wasn't... or if there was, that it wasn't relevant at all. Maybe you could've used a noise to give him an excuse to turn? Feels like a loose end otherwise, but overall I love the idea! Creepy stuff.
-cd-