"How are you supposed to know where Mecca is?"

Prisoner Zero stared at him.

"I thought people like you had to pray five times a day?"

Like me?

Only if they believe in God, Prisoner Zero wanted to say, but he didn't; believe in God or say it either. He believed in cold equations, Quantum Foam and in time, which he knew had two mutually compatible shapes. The first spiralled out like an ice-cream cone, widening in circles from a single point at the bottom, the other was spherical.

He'd chased down some of the equations twenty years before, thinking about little else towards the end and always reaching the same conclusion. Time was a marble.

A book had held his proof. A cheap notebook mostly full of songs, with tattered corners and a vomit stain across the back. Its final pages were brittle and wavy from cat pee, where Miu had got trapped indoors one weekend and been reduced to pissing on Prisoner Zero's notes and a pile of New Scientists in one corner. The nearest thing she could find to a litter tray.

That would have been the last summer in Amsterdam. The year Johnny Thunders issued Hurt Me on the New Rose label. The year of New England.

Emperors had killed themselves before, not often admittedly, although one famously threw himself off a cliff during a thunderstorm. And it was felt by many that the Librarian should have realized the cliff incident was about to happen, given that the old man had spent the previous week working himself up into thunder and lightning.

At which point, someone offered the belief that the Librarian had known exactly what was about to happen and chosen not to interfere. The resulting discussion about the nature of free will lasted for roughly eighty years and led to the colonization of a new world as a third of the inhabitants on a world in the equatorial belt took themselves off into exile.

No emperor had ever tried to starve himself, if this was what was happening, and there were arguments about that too. Some believed the latest Chuang Tzu was ill and should be treated or helped, and the feeling among these was that the Library should reach into the young man's mind to send him to sleep, working its magic while the Emperor was unable to harm himself. Others saw what was happening as a battle between the new Chuang Tzu and the Library itself. Although what they were fighting over and exactly what weapons were being used was open to debate.

And so Zaq found himself sitting with his back to his bed, the blade and tang held loosely in one hand. He'd taken to pissing against a pillar, as if he'd forgotten or no longer cared that an audience of billions might be watching. And while it was true that he still hid for the more serious ablutions he went to the commode alone, with none of the ceremony or retinue of attendants which usually accompanied him.

It was into this stalemate that a man climbed, scaling the outer walls of the Purple City as if he'd been practising all his life. He wore green trousers and a red shirt, black gloves and no shoes, the soles of his feet having been modified both to increase his grip and do away with the need for footwear. His hair was black and worn tied back, much like Zaq's own.

The man was in his twenties. A mere child in the eyes of most who watched his climb. Hardly anyone in the Servitors' City paid much attention to him at first. All the important people had been summoned by the palace master to discuss what could be created that was exquisite enough to bring the Emperor out of his depression.

As expected the first concubine, chief cook and head musician had very different opinions, although not one was able to suggest something that hadn't been tried a dozen times before.

And so the man walked between the low houses traditional to the Servitors' City until he reached the Manchu Gate, which led through the City of Ambassadors to the Tiananmen and Wu Gates, the last of which guarded the entrance to the palace.

In fact, "palace" was really a misnomer for a complex of temples, courtyards and yellow-roofed pavilions, surrounded by a wide moat which lapped gently against a walkway that ran along the bottom of the walls.

There were a thousand courtyards and nearly ten thousand rooms within the walled space of the Zigin Chéng, otherwise known as the Forbidden City. Of these, six pavilions, three gates and two bridges were significant and all of those were slung out along a north-south axis like fat weights on a fishing line.

The first of the important pavilions was the Qianquing, known as the Dragon Gong. It had a two-tiered roof that turned up at the corners and its walls were cinnabar red, both inside and out, while the wooden beams which supported its yellow-tiled roof were painted green and red, again as propriety required. At each corner of the roof, carved dragon acroteria protected the Chuang Tzu from evil spirits

Behind the Qiangquing was the Jiaotai Gong, where imperial seals were stored and the empress received homage. A small pavilion with a single roof lay behind this, where the empress slept and received the emperor, when there was an empress, which there wasn't.

These three pavilions made up the imperial quarters and were copies of larger, ceremonial buildings further south. And whereas the private buildings were raised from the ground on a simple marble platform, the great ceremonial pavilions of Preserving Harmony, Central Harmony and Supreme Harmony stood upon a triple platform. So that the very first brick of Supreme Harmony, the greatest of the halls, was four times the average height of an imperial soldier.

Begun in the fifteenth century, Earth era, on the site of an earlier city and laid out to strict Confucian lines, the original Forbidden City had taken fourteen years to build and required the toil of a hundred thousand artisans and the enslavement of a million Chinese peasants. No one knew how long it took the second Zigin Chéng to grow. There were a few who believed that acroteria, followed by yellow-glazed tiles, had twisted out of the ground like shoots from a seed.

And there were others who believed that the city formed itself overnight while the first Chuang Tzu slept: Although these were divided into those who believed the outer city was formed new and fell into disrepair and those who believed it grew ready-aged, some walls already crumbled and courtyards fallen into disrepair.

As with most things, the majority of the 2023 worlds' 148 billion inhabitants never gave the matter a single thought. The City of Ambassadors and the Servitors' City had been wrapped around the palace for over forty-five centuries and the palace had been wrapped around the beating heart of the emperor's pavilions for just as long.

Two hundred paces along the walkway, to the east of the Wu Gate, a sluice in the purple walls let through the Golden River, although iron bars closed off this route to all living creatures larger than a ten-year-old carp.

"Not for us." One glance at the bars and the man kept walking, his gaze on a corner turret a hundred paces beyond that. It was impressive, triple-tiered and almost a fortress in its own right. In its shadow, three fishermen in court robes were busy climbing into a flat-bottomed boat.

The man dressed as a servitor smiled at them politely and turned the corner, passing the East Gate, where a dragon arch fit for an emperor was flanked by a phoenix gate for his empress, with lesser entrances for everyone else, beginning with squared porches for civil and military administrators and ending with a simple wooden door that let such as him go about their business.

Nodding to a guard, the man walked on. Several hundred paces further along the walkway was the north-east corner turret.