The lighthouse at the end of the northern breakwater had been automated for almost forty years, but the town still sent someone out to it every Thursday. Nobody remembered who had made the rule, and nobody had ever written it down. It was simply understood that on Thursday afternoon, when the ferry had left and the fish market had been hosed clean, one person would walk the length of the stone pier, unlock the iron door with the key that hung behind the counter of the harbour office, climb the hundred and twelve steps, and look.

For most of that time the person had been Margaret Hale, who ran the chandlery and claimed she needed the exercise. When her knees finally gave out, the key passed to her grandson Tomas, who was fourteen and considered the whole business a waste of a perfectly good afternoon. He said so, loudly, for the first three weeks. On the fourth Thursday a storm came in early from the west, and he found himself at the top of the tower watching a small sailing boat fight its way past the outer rocks with a torn jib and nobody visibly at the helm.

He did what his grandmother had told him to do, which was nothing dramatic. He wrote down the time, the direction of the wind, the name painted on the stern, and the fact that he could see only one person on deck. Then he walked back down the hundred and twelve steps, crossed the pier with his hood pulled tight, and told the harbour master, who telephoned the lifeboat station. The boat was towed in an hour later. Its skipper, a retired schoolteacher who had been sailing alone from the islands, had broken his wrist when the boom swung across and had been steering with his feet.

The story was in the local paper the following week, and Tomas was embarrassed by it, mostly because the photograph showed him in his school uniform. What stayed with him was something else. On the walk back along the pier that evening, the harbour master had told him that the automated light had worked perfectly the whole time. It had turned, it had flashed its pattern, and it had done exactly what it was built to do. The light could warn a boat away from the rocks, but it could not notice that a boat was in trouble. Only a person could do that, and only if a person was there to look.

People in the town sometimes talk about that rule now as though it had been a clever piece of planning, a deliberate safeguard against the limits of machines. Tomas does not think it was anything of the kind. He thinks it began because somebody missed the old keeper and could not quite bring themselves to stop going out to the tower, and that it continued because nobody wanted to be the one to end it. Habits are like that. They outlast their reasons, and every so often, without anyone planning it, they find a new one.

He is twenty-six now and works as an engineer on the offshore wind farm that you can see from the top of the lighthouse on a clear day: two hundred white turbines standing in rows on the horizon, each one watched by sensors that report vibration, temperature and blade pitch to a control room in another country. The systems are very good. They catch almost everything. He still goes out to the tower on Thursdays when he is home, climbs the steps, and looks.

Ask him why, and he will tell you a story that has nothing to do with lighthouses. In his second year on the wind farm, a monitoring system flagged a slow rise in the temperature of a gearbox on one of the turbines at the far end of the array. The rise was small, well inside the limits, and the software ranked it as low priority. It would have been looked at during the next scheduled visit, six weeks later. A technician on the maintenance boat, passing the turbine on another job, noticed that the nacelle sounded different, a faint grinding note under the usual hum, and asked the skipper to stop. When they opened the gearbox they found a bearing that was a few days from failing. Replacing it cost a morning. Replacing the gearbox after the bearing failed would have cost a month and the price of a small house.

The technician was not cleverer than the software. She had simply been there, close enough to hear, and curious enough to ask for the boat to stop. The data had shown the same problem; it had just not shown it loudly enough for anyone to care. Tomas thinks about that often. Every system he has worked on has been very good at measuring the things its designers expected to go wrong, and much less good at the things nobody expected. The gap between the two is where people still earn their keep, not by doing the machine's job better than the machine, but by noticing when the job itself has quietly changed.

So on Thursdays, when he can, he walks out along the pier. The stone is worn smooth in a line down the middle where generations of boots have gone the same way. The iron door still sticks in wet weather. The view from the top has changed more in the last ten years than in the hundred before, and he likes to see it for himself.
