Then the light went out.

Vorbis's voice said, “Take the lead again.”

Trembling, Brutha obeyed. He felt the soft flesh of an outflung arm under his sandal for a moment.

The pit, he thought. Look into Vorbis's eyes, and there's the pit. And I'm in it with him.

I've got to remember about fundamental truth.

No more guides were patrolling the labyrinth. After a mere million years, the night air blew cool on his face, and Brutha stepped out under the stars.

“Well done. Can you remember the way to the gate?”

“Yes, Lord Vorbis.”

The deacon pulled his hood over his face.

“Carry on.”

There were a few torches lighting the streets, but Ephebe was not a city that stayed awake in darkness. A couple of passers-by paid them no attention.

“They guard their harbor,” said Vorbis, conversational. “But the way to the desert . . . everyone knows that no one can cross the desert. I am sure you know that, Brutha.”

“But now I suspect that what I know is not the truth,” said Brutha.

“Quite so. Ah. The gate. I believe it had two guards yesterday?”

“I saw two.”

“And now it is night and the gate is shut. But there will be a watchman. Wait here.”

Vorbis disappeared into the gloom. After a while there was a muffled conversation. Brutha stared straight ahead of him.

The conversation was followed by muffled silence. After a while Brutha started to count to himself.

After ten, I'll go back.

Another ten, then.

All right. Make it thirty. And then I'll . . .

“Ah, Brutha. Let us go.”

Brutha swallowed his heart again, and turned slowly.

“I did not hear you, lord,” he managed.

“I walk softly.”

“Is there a watchman?”

“Not now. Come help me with the bolts.”

A small wicket gate was set into the main gate. Brutha, his mind numb with hatred, shoved the bolts aside with the heel of his hand. The door opened with barely a creak.

Outside there was the occasional light of a distant farm, and crowding darkness.

Then the darkness poured in.

Hierarchy, Vorbis said later. The Ephebians didn't think in terms of hierarchies.

No army could cross the desert. But maybe a small army could get a quarter of the way, and leave a cache of water. And do that several times. And another small army could use part of that cache to go further, maybe reach halfway, and leave a cache. And another small army . . .

It had taken months. A third of the men had died, of heat and dehydration and wild animals and worse things, the worse things that the desert held . . .

You had to have a mind like Vorbis's to plan it.

And plan it early. Men were already dying in the desert before Brother Murduck went to preach; there was already a beaten track when the Omnian fleet burned in the bay before Ephebe.

You had to have a mind like Vorbis's to plan your retaliation before your attack.

It was over in less than an hour. The fundamental truth was that the handful of Ephebian guards in the palace had no chance at all.

Vorbis sat upright in the Tyrant's chair. It was ap?proaching midnight.

A collection of Ephebian citizens, the Tyrant among them, had been herded in front of him.

He busied himself with some paperwork and then looked up with an air of mild surprise, as if he'd been completely unaware that fifty people were waiting in front of him at crossbow point.

“Ah,” he said, and flashed a little smile.

“Well,” he said, “I am pleased to say that we can now dispense with the peace treaty. Quite unneces?sary. Why prattle of peace when there is no more war? Ephebe is now a diocese of Omnia. There will be no argument.”

He threw a paper on to the floor.

“There will be a fleet here in a few days. There will be no opposition, while we hold the palace. Your in?fernal mirror is even now being smashed.”

He steepled his fingers and looked at the assembled Ephebians.

“Who built it?”

The Tyrant looked up.

“It was an Ephebian construction,” he said.

“Ah,” said Vorbis, “democracy. I forgot. Then who”-he signaled one of the guards, who handed him a sack-“wrote this?”

A copy of De Chelonian Mobile was flung on to the marble floor.

Brutha stood beside the throne. It was where he had been told to stand.

He'd looked into the pit and now it was him. Every?thing around him was happening in some distant cir?cle of light, surrounded by darkness. Thoughts chased one another round his head.

Did the Cenobiarch know about this? Did anyone else know about the two kinds of truth? Who else knew that Vorbis was fighting both sides of a war, like a child playing with soldiers? Was it really wrong if it was for the greater glory of . . .

. . . a god who was a tortoise. A god that only Brutha believed in?

Who did Vorbis talk to when he prayed?

Through the mental storm Brutha heard Vorbis's level tones: “If the philosopher who wrote this does not own up, the entirety of you will be put to the flame. Do not doubt that I mean it.”

There was a movement in the crowd, and the sound of Didactylos's voice.

“Let go! You heard him! Anyway . . . I always wanted a chance to do this . . .”

A couple of servants were pushed aside and the philosopher stumped out of the crowd, his barren lan?tern held defiantly over his head.

Brutha watched the philosopher pause for a mo?ment in the empty space, and then turn very slowly until he was directly facing Vorbis. He took a few steps forward then, and held the lantern out as he appeared to regard the deacon critically.

“Hmm,” he said.

“You are the . . . perpetrator?” said Vorbis.

“Indeed. Didactylos is my name.”

“You are blind?”

“Only as far as vision is concerned, my lord.”

“Yet you carry a lantern,” said Vorbis. “Doubtless for some catchword reason. Probably you'll tell me you're looking for an honest man?”

“I don't know, my lord. Perhaps you could tell me what he looks like?”

“I should strike you down now,” said Vorbis.

“Oh, certainly.”

Vorbis indicated the book.

“These lies. This scandal. This . . . this lure to drag the minds of men from the path of true knowl?edge. You dare to stand before me and declare”-he pushed the book with a toe-“that the world is flat and travels through the void on the back of a giant turtle?”

Brutha held his breath.

So did history.

Affirm your belief, Brutha thought. Just once, someone please stand up to Vorbis. I can't. But some?one . . .

He found his eyes swiveling toward Simony, who stood on the other side of Vorbis's chair. The sergeant looked transfixed, fascinated.

Didactylos drew himself up to his full height. He half-turned and for a moment his blank gaze passed across Brutha. The lantern was extended at arm's length.

“No,” he said.

“When every honest man knows that the world is a sphere, a perfect shape, bound to spin around the sphere of the Sun as Man orbits the central truth of Om,” said Vorbis, "and the stars-

Brutha leaned forward, heart pounding.

“My lord?” he whispered.

“What?” snapped Vorbis.

“He said `no,' ” said Brutha.

“That's right,” said Didactylos.

Vorbis sat absolutely motionless for a moment.

Then his jaw moved a fraction, as if he was rehearsing some words under his breath.

“You deny it?” he said.

“Let it be a sphere,” said Didactylos. “No problem with a sphere. No doubt special arrangements are made for everything to stay on. And the Sun can be another larger sphere, a long way off. Would you like the Moon to orbit the world or the Sun? I advise the world. More hierarchical, and a splendid example to us all.”

Brutha was seeing something he'd never seen be?fore. Vorbis was looking bewildered.

“But you wrote . . . you said the world is on the back of a giant turtle! You gave the turtle a name!”

Didactylos shrugged. “Now I know better,” he said. “Who ever heard of a turtle ten thousand miles long? Swimming through the emptiness of space? Hah. For stupidity! I am embarrassed to think of it now.”

Vorbis shut his mouth. Then he opened it again.

“This is how an Ephebian philosopher behaves?” he said.

Didactylos shrugged again. “It is how any true phi?losopher behaves,” he said. “One must always be ready to embrace new ideas, take account of new proofs. Don't you agree? And you have brought us many new points”-a gesture seemed to take in, quite by accident, the Omnian bowmen around the room?-“for me to ponder. I can always be swayed by power?ful argument.”

“Your lies have already poisoned the world!”

“Then I shall write another book,” said Didactylos calmly. “Think how it will look-proud Didactylos swayed by the arguments of the Omnians. A full re?traction. Hmm? In fact, with your permission, lord-I know you have much to do, looting and burning and so on-I will retire to my barrel right away and start work on it. A universe of spheres. Balls spinning through space. Hmm. Yes. With your permission, lord, I will write you more balls than you can imagine . . .”

The old philosopher turned and, very slowly, walked towards the exit.

Vorbis watched him go.

Brutha saw him half-raise his hand to signal the guards, and then lower it again.

Vorbis turned to the Tyrant.

“So much for your-” he began.

“Coo-ee!”

The lantern sailed through the doorway and shattered against Vorbis's skull.

“Nevertheless . . . the Turtle Moves!”

Vorbis leapt to his feet.

“I- he screamed, and then got a grip on himself. He waved irritably at a couple of the guards. ”I want him caught. Now. And . . . Brutha?"

Brutha could hardly hear him for the rush of blood in his ears. Didactylos had been a better thinker than he'd thought.

“Yes, lord?”

“You will take a party of men, and you will take them to the Library . . . and then, Brutha, you will burn the Library.”

Didactylos was blind, but it was dark. The pursuing guards could see, except that there was nothing to see by. And they hadn't spent their lives wandering the twisty, uneven and above all many-stepped lanes of Ephebe.

“-eight, nine, ten, eleven,” muttered the philosopher, bounding up a pitch-dark flight of steps and haring around a corner.

“Argh, ow, that was my knee,” muttered most of the guards, in a heap about halfway up.

One made it to the top, though. By starlight he could just make out the skinny figure, bounding madly along the street. He raised his crossbow. The old fool wasn't even dodging . . .

A perfect target.

There was a twang.

The guard looked puzzled for a moment. The bow toppled from his hands, firing itself as it hit the cobbles and sending its bolt ricocheting off a statue. He looked down at the feathered shaft sticking out of his chest, and then at the figure detaching itself from the shadows.

“Sergeant Simony?” he whispered.

“I'm sorry,” said Simony. “I really am. But the Truth is important.”

The soldier opened his mouth to give his opinion of the truth and then slumped forward.