He stepped out into his shop, and stopped.

“Oh… I'm so sorry to have kept you,” he said. It was a woman. And two trolls had taken up positions just inside the door. Their dark glasses and huge ill-fitting black suits put them down as people who put people down. One of them cracked his knuckles when he saw Jeremy looking at him.

The woman was wrapped in an enormous and expensive white fur coat, which might have explained the trolls. Long black hair cascaded over her shoulders, and her face was made up so pale that it was almost the shade of the coat. She was… quite attractive, thought Jeremy, who was admittedly no judge whatsoever, but it was a monochromatic beauty. He wondered if she was a zombie. There were quite a few in the city now, and the prudent ones had taken it with them when they died, and probably could afford a coat like that.

“A beetle clock?” she said. She had turned away from the glass dome.

“Oh, er, yes… The Hershebian lawyer beetle has a very consistent daily routine,” said Jeremy. “I, er, only keep it for, um, interest.”

“How very… organic,” said the woman. She stared at him as if he was another kind of beetle. “We are Myria LeJean. Lady Myria LeJean.”

Jeremy obediently held out a hand. Patient men at the Clockmakers' Guild had spent a long time teaching him how to Relate to People before giving it up in despair, but some things had stuck.

Her ladyship looked at the waiting hand. Finally, one of the trolls lumbered over.

“Der lady does not shake hands,” it said, in a reverberating whisper. “She are not a tactile kinda person.”

“Oh?” said Jeremy.

“But enough of this, perhaps,” said Lady LeJean, stepping back. “You make clocks, and we—”

There was a jingling noise from Jeremy's shirt pocket. He pulled out a large watch.

“If that was chiming the hour, you are fast,” said the woman.

“Er… um… no… you might find it a good idea to, um, put your hands over your ears…”

It was three o'clock. And every clock struck it at once. Cuckoos cuckooed, the hour pins fell out of the candle clock, the water clocks gurgled and seesawed as the buckets emptied, bells clanged, gongs banged, chimes tinkled and the Hershebian lawyer beetle turned a somersault.

The trolls had clapped their huge hands over their ears, but Lady LeJean merely stood with her hands on her hips, head on one side, until the last echo died away.

“All correct, we see,” she said.

“What?” said Jeremy. He'd been thinking: perhaps a vampire, then?

“You keep all your clocks at the right time,” said Lady LeJean. “You're very particular about that, Mr Jeremy?”

“A clock that doesn't tell the right time is… wrong,” said Jeremy. Now he was wishing she'd go away. Her eyes were worrying him. He'd heard about people having grey eyes, and her eyes were grey, like the eyes of a blind person, but she was clearly looking at him and through him.

“Yes, there was a little bit of trouble over that, wasn't there?” said Lady LeJean.

“I… I don't… I don't… don't know what you're—”

“At the Clockmakers' Guild? Williamson, who kept his clock five minutes fast? And you—”

“I am much better now,” said Jeremy stiffly. “I have medicine. The Guild was very kind. Now please go away.”

“Mr Jeremy, we want you to build us a clock that is accurate.”

“All my clocks are accurate,” said Jeremy, staring at his feet. He wasn't due to take his medicine for another five hours and seventeen minutes, but he was feeling the need for it now. “And now I must ask—”

“How accurate are your clocks?”

“Better than a second in eleven months,” said Jeremy promptly.

“That is very good?”

“Yes.” It had been very good. That was why the Guild had been so understanding. Genius is always allowed some leeway, once the hammer has been pried from its hands and the blood has been cleaned up.

“We want much better accuracy than that.”

“It can't be done.”

“Oh? You mean that you can't do it?”

“No, I can't. And if I can't, then neither can any other clockmaker in the city. I'd know about it if they could!”

“So proud? Are you sure?”

“I'd know.” And he would. He'd know for certain. The candle clocks and the water clocks… they were toys, which he kept out of a sort of respect for the early days of timekeeping, and even then he'd spent weeks experimenting with waxes and buckets and had turned out primitive clocks that you could, well, very nearly set your watch by. It was okay that they couldn't be that accurate. They were simple, organic things, parodies of time. They didn't grind across his nerves. But a real clock… well, that was a mechanism, a thing of numbers, and numbers had to be perfect.

She put her head on one side again. “How do you test to that accuracy?” she said.

They'd often asked him that in the Guild, once his talent had revealed itself. He hadn't been able to answer the question then, either, because it didn't make sense. You built a clock to be accurate. A portrait painter painted a picture. If it looked like the subject, then it was an accurate picture. If you built the clock right, it would be accurate. You didn't have to test it. You'd know.

“I'd know,” he said.

“We want you to build a clock that is very accurate.”

“How accurate?”

“Accurate.”

“But I can only build to the limit of my materials,” said Jeremy. “I have… developed certain techniques, but there are things like… the vibration of the traffic in the street, little changes in temperature, that sort of thing.”

Lady LeJean was now inspecting a range of fat imp-powered watches. She picked one up and opened the back. There was the tiny saddle, and the pedals, but they were forlorn and empty.

“No imps?” she said.

“I keep them for historical interest,” said Jeremy. “They were barely accurate to a few seconds a minute, and they'd stop completely overnight. They were only any good if your idea of accuracy was ‘around two-ish’.” He grimaced when he used the term. It felt like hearing fingernails on a blackboard.

“How about invar?” said the lady, still apparently inspecting the museum of clocks.

Jeremy looked shocked. “The alloy? I didn't think anyone outside the Guild knew about that. And it is very expensive. Worth a lot more than its weight in gold.”

Lady LeJean straightened up. “Money is no object,” she said. “Would invar allow you to reach total accuracy?”

“No. I already use it. It's true that it is not affected by temperature, but there are always… barriers. Smaller and smaller interferences become bigger and bigger problems. It's Xeno's Paradox.”

“Ah, yes. He was the Ephebian philosopher who said you couldn't hit a running man with an arrow, wasn't he?” said the lady.

“In theory, because—”

“But Xeno came up with four paradoxes, I believe,” said Lady LeJean. “They involved the idea that there is such a thing as the smallest possible unit of time. And it must exist, mustn't it? Consider the present. It must have a length, because one end of it is connected to the past and the other is connected to the future, and if it didn't have a length then the present couldn't exist at all. There would be no time for it to be the present in.”

Jeremy was suddenly in love. He hadn't felt like this since he'd taken the back off the nursery clock when he was fourteen months old.

“Then you're talking about… the famous ‘tick of the universe’,” he said. “And no gear cutter could possibly make gears that small…”

“It depends on what you would call a gear. Have you read this?”

Lady LeJean waved a hand at one of the trolls, who lumbered over and dropped an oblong package on the counter.

Jeremy undid it. It contained a small book. “Grim Fairy Tales?” he said.