A scrape of leather sole on concrete was all the warning Moz got of an anger so tight that Hassan tried to keep it silent.

Five... four... three... two...

Twisting sideways, Moz ducked. Only not quite fast enough because Hassan's left fist caught the side of his head and dropped Moz to one knee.

"Stop it!"

Malika's plea reached Moz through swimming darkness. And as Hassan positioned himself in front of Moz, the kneeling boy was faced with a flash of expensive clothes, smoky buttons on a cotton shirt. A belt of tan leather with dark spots in it. Black leather loafers that settled themselves and then moved again as Hassan prepared himself for a kick.

"No!" Malika shouted.

Indeed not.

Almost absent-mindedly, Moz reached forward and found the older boy's testicles, soft plums wrapped in silk. For a moment he was tempted to crush them but instead he made do with a cloth-creasing twist. And it was Moz who kicked, though first he had to force himself to his feet.

It was a blow weighted with years of anger, a fat crystal of cooking speed and frustration that Malika's sulkiness had somehow soured what Moz felt for Celia.

"Moz!" Malika said.

He heard her but Moz kicked just the same, feeling his toes curl as they sunk into Hassan's stomach.

Everyone in the street halted like God froze time and then Georgiou burst from the café, a cloth still in one hand.

"What are you doing?"

Moz expected Hassan to buckle over and fall to his knees, clutching his gut. And that later when Hassan had recovered, he'd round up Idries and some of the others and come looking for Moz, making the streets around Riad al-Razor a bad place to be for a few weeks, maybe even a month or so.

What actually happened was that vomit sprayed from Hassan's mouth. A fountain of black coffee, mint tea and half-digested cake splashing onto Moz and making Malika step back with a jump. And the stench as Hassan crumpled to his knees suggested this wasn't the only orifice to void.

"Shit," said Georgiou, suddenly sounding distinctly local.

"I reckon so," said Moz.

CHAPTER 27

Lampedusa, Wednesday 4 July [Now]

"Whatever." It would have to do.

Using a square of cigarette packet, Prisoner Zero smeared his stink along the base of a wall, filling the gaps. They were going to kill him before he had time to skim all the walls; the prisoner had worked this out around dawn.

"Prisoner Zero."

It was a sergeant. One who didn't like him, as opposed to Master Sergeant Saez, who actually hated him. Prisoner Zero found it hard to tell Saez and Kovacs apart because both had bull necks, cropped hair, skin ripe like midnight and similar thousand-klick stares. What Prisoner Zero saw when he looked at the two marines was not their scowls or skin tone, but uniforms.

They both wore a weird kind of jungle fatigue. Something mud-coloured, like it was designed for a forest where everything had begun to die. Unless, of course, it was meant to be desert camouflage, in which case it matched no stretch of sand or gravel Prisoner Zero had ever seen.

He was meant to stand now. This had been explained to him.

Master Sergeant Saez would come in first and shout his name, Prisoner Zero then had to stand, stare straight ahead and stay silent unless spoken to. This last part was easy enough. As for the rest... Sergeant Saez continued to demand that he come to attention but had long since stopped believing it was going to happen.

Knocking someone down was easy. Making them stand up to order was far more difficult.

"Attention."

Prisoner Zero turned his back on the noise of his cage being unlocked and concentrated instead on the square of cardboard as it skimmed over mesh in confident sweeps. Small rebellions were all he had left.

The outraged shouts never came. Instead Prisoner Zero became aware that someone stood right behind him, watching. Tossing aside his cardboard paddle, Prisoner Zero paused to admire the result. Something was still missing, that much was obvious. Unfortunately, he was having trouble working out what.

"Fermat," said Katie Petrov.

"You're right," a voice said, sounding impressed. The owner of the voice was a balding Italian in grey uniform. He was probably of normal build and height, but standing between Sergeants Saez and Kovacs, he looked both short and thin. Wire rim glasses magnified washed-out blue eyes.

"I'm Dr. Angelo," said the man in Arabic. "Have you finished?" Elegant fingers gestured at shit smeared across the wall of the cage. "If not, then please do."

Sergeant Kovacs had taken away Prisoner Zero's stub of wire the previous evening during an unscheduled search of his cage. This was one of the reasons the prisoner was behind. It had taken him most of the night to find a loose weld and work free a stubby length of wire.

Producing the wire from his mouth, Prisoner Zero slashed an equation into the lattice. It was famous and he used it only to fill space, adding a less famous equation (which was at least two centuries older) and improvised a third which linked the first two.

The fourth was something he'd stumbled over on his knees beside a canal. He'd lost his job by then, Prisoner Zero was pretty sure of it. There were some limits to life tenure, even at the University of Amsterdam. So much unfinished. He guessed God probably felt like that.

And so Prisoner Zero began to sketch. A circle, multi-layered, each layer actually a circle seen from the side so that it looked like a line, except each of these circles was really a sphere. Only he lacked the ability to express that extra dimension except in his head. So he drew another circle alongside the first and separated them with a vertical line to remind himself that they were the same but not.

He did this part mostly from the memory of a few pages at the back of an exercise book, the middle pages being taken up with chord changes for songs that never got written, much less recorded.

"What is it?" Katie Petrov asked.

"A butterfly," said the uniformed Italian.

"This is Vice Questore Pier Angelo," said Katie. "He's been asked to examine you."

"If that's all right?" said the Vice Questore. For a foreigner his Arabic seemed pretty good.

"I've worked for the UN," said the man. "In Baghdad and Damascus." Nodding to Master Sergeant Saez, who stood with a rifle clutched to his chest and a scowl souring his heavy face, Vice Questore Angelo added, "I'm also a Marxist, one of the few left. That's why your friend doesn't like me."

Katie Petrov smiled. "You want any help?"

"No." The balding man shook his head. "What I want is this room emptied while I make my examination." He had the face of a well-bred horse, with what was left of his hair swept back like a mane behind his ears. A wedding ring on his second finger said Katie Petrov's first impression was wrong.

"You don't need me to stay?"

"No," said the Vice Questore. "I'll need the patient out of his cage and the room to myself. I don't start until that happens."

"It's going to be a long wait," said Sergeant Kovacs.

Turning his back on their squabble, Prisoner Zero examined his work and discovered that it was already dead. The sketches, formulae and equations just looked what they were, simple cold equations signifying nothing. His map of space where ice held memories and the darkness spoke in miracles was gone.

"That's better," said the Vice Questore when the door to the weights room finally shut. Popping open his black leather bag, he extracted a stethoscope, a pair of surgical gloves and a small flashlight.

"Katie Petrov demanded a local doctor. Luckily I was in the area. Dr. Petrov and I came to a mutually advantageous agreement..." There was, of course, no luck involved at all. Vice Questore Pier Angelo took a look at the cage and decided it was every bit as bad as Rome had been led to believe.