He had no luck in getting the attendants to brew or distil something alcoholic from the kitchens" supplies. And he never had found that open door again, or any open door. All of them were closed and locked these days. The last interesting thing he'd found was another stupid joke, and one he didn't even fully understand.

He'd been deep in the castle's lower levels, looking for the door, or for the small attendant who had discovered him in the room (he still had dreams about those alien brown arms, that blue sky with the contrail across it; that sun!), and he had heard a steady, monotonous thumping noise far away, down a network of tunnels and corridors.

He followed the pounding sound until he came to an area where the floors of the corridors and alcoves were covered with fine grey dust, and the air was hazed with the same dry stuff. The floor shook rhythmically to the pounding. He went down some broad, worn steps to a cross-corridor, and sneezed on the dust.

A small attendant wearing grey boots and no cowl-brim scuttled along the broad corridor the steps led down to. It stopped when it saw him.

"Can I help you?" it squeaked. Its voice was very high, but at least it was civil. Quiss decided to take advantage of this.

"Yes, you can," he said, holding a bit of his furs over his mouth and nose to keep the swirling dust out. His eyes smarted. The pounding was closer, down the corridor where large double doors faced him. "What the hell's that noise? Where's all this dust come from?"

The attendant regarded him quietly for a moment, then said, "Come with me." It walked off towards the double doors. Quiss followed. The double doors were made out of plastic, with clear plastic inserts at about human head-level. On one of the doors there was a large symbol like this: D. It reminded Quiss of a half-moon. On the other door, the right-hand one, there was this symbol: P. The attendant swept through the doors in a cloud of dust. Coughing, holding the furs tighter over his mouth, Quiss held one door open and looked through.

Inside a huge cavern of a room, hundreds of minions scurried about in the grey mist. There were conveyor belts, overhead cranes and hoppers, buckets and wheelbarrows, and a narrow-gauge railway system with rails - where they could be seen through the piles and drifts of dust - which looked very similar to those Quiss had noticed in the castle kitchens. The whole place was filled with clouds of fine grey swirling dust, and shook and echoed to the continuous pounding, crashing noise he had heard more distantly earlier. The noise was being produced by a single gigantic machine in the very centre of the room. The machine appeared to be made up largely of great man-thick metal columns, tangles of wire and cables, and a cagework of constantly rising and falling gates of metal mesh.

In the centre of the machine something massive-looking flashed silver in time to the pounding noise. Above the centre of the machine, also in time to the beat, a silver metal cylinder rose and fell. Grey, oddly crafted blocks or sculptures went in at one side of the machine; dust blew out at the other side. Dust and rubble. The rubble was carried away on a conveyor belt to huge vats Quiss could just make out in the powder-hazed distance. The dust was apparently meant to be sucked up by extractor ducts in the ceiling (again, similar to the system in the kitchens), but a lot of the dust seemed to be evading the intakes. Quiss could see - through all the dust in the air - great drifts of it piled like frozen waves around vats and conveyor belt housings. In several places grey-booted minions were shovelling the grey dust into wheelbarrows or small hopper-like wagons on the narrow-gauge railways. Other minions were wheeling full, grey-heaped barrows up perilously narrow planks and gantries to the lips of the giant vats, and tipping the dust in; a lot of it billowed out again.

As far as Quiss could make out in the grey gloom, from the vats large overhead buckets scooped up grey, viscous fluid, which was poured into moulds on conveyor belts which disappeared into long, hissing machines; at the far end of the machines the moulds were stripped off the grey sculptures which were then minion-handled or trolleyed to another conveyor belt which led into the pounding machine in the centre of the room...

"What in hell's name is this?" Quiss said incredulously, choking on the dust.

"This is dee pee," the attendant said primly, standing in front of him, arms folded. "This is the nerve centre of the entire castle. Without us, the whole place would simply grind to a halt." It sounded proud.

"Are you sure?" Quiss said, coughing. The minion stiffened.

"Have you any other questions?" it said coldly. Quiss was looking at the objects which he thought of as sculptures as they moved steadily along the conveyor belt to their destruction. They were funny shapes: 5, 9, 2, 3,4...

"Yes," he said, pointing at the shapes, "what are those meant to be?"

"Those are," the attendant said pointedly, "numbers."

"Don't look like numbers to me," Quiss said.

"Well, they are," the minion said impatiently. That's the whole point."

"The whole point of what?" Quiss said, laughing and choking in almost equal parts. He could see he was annoying the small minion, and thought this was good fun. He'd certainly never seen numbers that shape before, but of course they could easily be numbers in some alien language or system. Ajayi might even have recognised them.

"The whole point of what we're doing here," the attendant said, as though trying to be more patient than it really felt. "This is the number-crunching room. Those are numbers," it said, enunciating clearly as though for some small and wilfully obtuse child, and motioning behind it to the conveyor belt with one arm, "and this is where we crunch them. That machine is a number-cruncher."

"You're crazy," Quiss said into the fur over his mouth.

"What?" the attendant said, stiffening still further and then jolting forward, drawing itself up to its full - if still modest - height. Quiss coughed.

"Nothing. What do you make the numbers out of? What's that grey stuff?"

"Plaster of Salt Lake City," the minion said, as though only an idiot would ask such a question. Quiss frowned.

"What the hell's that?"

"It's like Plaster of Paris, except duller," the minion said, then turned and stamped off through the drifts of grey powder. Quiss shook his head, coughed, then let the plastic doors swing to.

Ajayi was still looking at the board and her two remaining tiles, staring from one to the other. Then she put her elbows on her knees, her chin in her hands, and closed her eyes, looking thoughtful.

The snow collected in the thin grey hairs of her head, but she still did not notice it was snowing. Her expression of concentration intensified. They were nearly finished.

Chinese Scrabble was played on a gridded board, a little like an infinitely small square section of the Go board they had played on hundreds of days ago, but in Chinese Scrabble one placed small tiles with pictograms on them into the squares formed by the grid of lines, not small stones on the interstices. They hadn't needed to come up with any complicated things like infinitely long pieces this time, but the problem had been the choice of pictograms they had been saddled with at the start of the game. Apart from anything else, they had had to learn a language called Chinese.

That alone had taken them over seven hundred days. Quiss had nearly given in several times, but Ajayi kept him going somehow; the new language excited her. It was a key, she said. Now she read even more.

Ajayi opened her eyes and studied the board again.

The meanings and possibilities of the pictograms in front of her filled her mind as she tried to fit the last two tiles somewhere into the network of skewed pathways she and Quiss had created on the small board.