[You look out the window every day, only for the window to start watching you?]
The protagonist has been cooped up at home for three months, passing the time by watching the nine windows across the street.
Nine neighbors, nine secrets.
Then one day, a window disappears, another has a note taped to it, and a letter arrives without a sound:
“You are the tenth window.”
He used to be the one keeping records. Now he is the one being watched.