The house on Mercer Street had been empty since before I moved in. The realtor mentioned it once, in passing, the way you mention a pothole you have learned to drive around.
For eleven years nothing happened there. The grass grew, someone cut it. The gutters filled, someone cleared them. Nobody ever saw who.
Then, on a Tuesday in October, the porch light came on at 2:14 in the morning.
I know the time because I was awake, and because the light came through my bedroom window at an angle that made the ceiling look like a page. It stayed on for eleven minutes. Then it went out.
The next night it happened again. And the night after that.
I started keeping a notebook. Within a week I had a pattern: 2:14, eleven minutes, no exceptions. Within two weeks I had something worse — a list of the nights it did not happen. Three nights, all of them nights I had been awake and watching.
By the end of the month I understood the shape of the thing, which is the problem with paying attention. The light only came on when I was watching.