I only bought the camera to watch the cat eat. One slow Tuesday afternoon I opened the app and saw a woman I had never met walking through my living room.

She pointed at a pub by the train station and asked one small, strange question. Weeks later I understood why it had snagged in my mind like a splinter.

I found his old Fitbit in a drawer. It synced to my phone and showed the truth: he was never working night shifts.

He set up a shared photo album so the whole family could post vacation pictures. One morning a new photo appeared that nobody in the family had taken.

The reflection in the TV screen showed a woman tying her shoes at the foot of his bed.

From a hotel room three time zones away, I flicked our living room lights on and off just to make him laugh. He didn't laugh. He called me screaming.