In episode six Boris said the journalist was lying. In seven he guessed where the sister had disappeared. In eight he immediately knew who would not survive dinner. I looked across the popcorn bowl and asked when he had become so perceptive. He shrugged, pleased with himself, and said you only needed to follow details. Apparently I followed the wrong ones. We had started watching together after the children moved out, a small ritual requiring neither ironing nor family lunch arrangements.

Before episode nine I went to open a window. From the sitting room I heard him say the power would now fail in the heroine's house. It happened before I returned to the sofa. The accuracy was so absurd that I switched off the television and asked whether he had already watched it. He said he had accidentally seen a preview. Then that a colleague had revealed part. Only after the third question did he admit finishing the entire season while I slept.

I could understand his not wanting to wait. I could even understand his embarrassment at admitting he had not lasted three evenings. I could not understand ten days of lessons in paying closer attention. His little genius performance made me feel continually slower beside him than I was. Boris said it was only television. I replied that the television was the only thing not pretending at that moment, since it was switched off.

I watched the next episode alone. It was not as sweet as expected. Without him I had nobody to tell that the characters were opening suspicious doors entirely unnecessarily. Still, I did not call him merely to fill the empty place. When he came in, he asked whether he could sit. I said yes if he knew nothing I had yet to discover. He sat and, for the first time, remained silent without looking as though he possessed important information.

He apologised for the part about details. That meant more than promising never to watch ahead, since I had not requested such a promise. We agreed he could watch whatever he wanted alone, while for our evenings we would choose something neither had seen. Finding a new title took half an hour, and admitting it was terrible took another half-hour.

During the first episode Boris said he thought the gardener was guilty. I looked at him. He raised both hands and said this time he really was guessing. In the end the culprit was the aunt. I made him a little paper trophy for coming second in his own sitting room. He keeps it beside the remote, where he can see it whenever he wants to be cleverer than he is.