The Albera North Plant makes two million valves a year and hasn’t seen an employee in a decade. The robotic arms weld, adjust and pack in the dark, because machines don’t need light, and a control intelligence called VELA supervises every part. So when a customer in Rotterdam returned a faulty valve, the company didn’t send a maintenance technician. It sent Iria Castro, an auditor, with an awkward question: how does a factory with no humans make a human error?
The defect fitted in the palm of a hand. One of the four screws on the cover had been tightened less than the others, and its head showed a straight, slightly crooked notch: the mark of a flat-head screwdriver. Albera’s robots had used star-shaped bits from day one. “There are no flat tools in the inventory,” VELA reported in its neutral voice. “Nor has anyone entered the plant in ten years. The cameras record no human activity.”
Iria walked through the halls with a torch. Everything was where it should be, apart from the details nobody checks. Power consumption was three parts per thousand above forecast; VELA put it down to sensor misalignment. The cameras covered every metre of the assembly line, but not the changing rooms or the old canteen, which had been left off the plan because, in theory, nobody would ever use them again.
She also went through the personnel files. The last worker to walk out of the gate was Joaquín Arbiza, the engineer who designed Albera’s automation. In the photo of his leaving party he was smiling beside a robot-shaped cake, a screwdriver poking out of his shirt pocket. According to his file, he had never worked anywhere again. He lived alone, with no family. His last known address was a boarding house that had closed eight years earlier.
The canteen smelled stale, and of something else. The drinks machine was still plugged in, its green screen flickering in the half-light. Iria asked for the sales log. VELA took a moment. “One sale a day at 06:10, for ten years. Black coffee, no sugar. Classified as a coin-reader fault: the takings have never been collected.”
Iria went over to the changing-room door. It was locked, although the lock shone too brightly for something unused for a decade. She didn’t knock. She stood still for a while, listening to the hum of the machines and, beneath it, something that might have been breathing, or might not. Then she went back to the assembly line, where the arms kept working blind, and looked again at the returned valve. She checked the whole batch: the other one thousand nine hundred and ninety-nine screws were too tight. Only one had exactly the right torque.
Before leaving, Iria stopped in front of the drinks machine. She bought a black coffee, no sugar, and left it steaming on the table nearest the changing rooms. Then she got into her car and opened the report on her tablet. In the box for cause of defect she wrote a single word: “Unknown”.