The sirens wailed into life at dusk, as darkness descended over the prison like a denial. In the prisoners’ quarters, a dense jungle of bunk beds and washbasins, the inmates returned their playing cards to the deck and trudged outside. Over in the mess hall, there was a loud clatter as the prisoners on cleaning duty dropped their dirty pots and pans and hurriedly dried their hands. The alarm even reached down beneath the chapel floor, where two boys were painstakingly tunnelling through the ground – nudging each other, they wiped the grime from their faces and began scrabbling back towards the surface. In a matter of minutes, all the inmates had gathered in the exercise yard, shivering in the cold as they waited for the evening headcount to begin.

All the inmates bar one.

In a tower above the guards’ barracks, the Traitor walked up a flight of stone steps; soft, deliberate footfalls untroubled by guilt. There was a crackle of loudspeakers, and then a high-pitched voice rang out above the siren: Attention! One minute until roll call! Any prisoners who fail to present themselves will be subject to one week in the punishment cells! The inmates responded with a rowdy chorus of boos and jeers. The Traitor smiled.

The stairwell was steep, and coiled like a serpent. The Traitor had spent hours hiding in a disused cellar beneath the guards’ quarters, and it felt good to be moving again. It had taken an age for the siren to announce the roll call, and then for the scrape of chair legs and the thunderous tread of jackboots above the Traitor’s head to mark the guards’ exit from the barracks. Waiting until the coast was clear, the Traitor had crept out of the cellar and moved soundlessly through the empty building. Steam rose from half-drained cups of coffee; books were jammed open on chair arms. A snooker table had been abandoned mid-game, leaving balls strewn across the scuffed green baize.

At the tower’s summit, the staircase came to an abrupt end at a door. The Traitor knocked twice, and entered a study dominated by a burnished desk and a phalanx of pockmarked metal filing cabinets. A couple of dusty books lay supine on a shelf on the far wall. The air was filled with smoke, the atmosphere heavy with the burden of countless cigarettes.

Mr Pitt stood stiffly by the window, his back as straight as a baton. The Traitor was aware how scared the other inmates were of this man – how Mr Pitt strode, bloody-knuckled, through their dreams. The Traitor wasn’t scared of him, though. The Traitor wasn’t scared of anything.

“You wanted to see me?”

Mr Pitt didn’t turn around. “Who am I?” he asked finally.

The Traitor paused, taken aback by the question. “You’re Mr Pitt, sir. The Assistant Chief Warder.”

Mr Pitt nodded. “I thought that once, too.” He removed a monocle from his eye and gave it a thorough wipe in a white handkerchief, still staring out of the window. The distant bark of the guards carried up to the study as they herded the prisoners into formation in the exercise yard. “But, as the years have gone by, as the centuries have amassed out here in no-time, I have realized that my official rank is meaningless. I am not the Assistant Chief Warder. I am not a prison officer of any stripe or description. I am a zookeeper. Overseeing a menagerie of rats.” He spat out the word as though it had curdled in his mouth, before continuing calmly: “Now, in all civilized cultures, rats are considered a pestilent menace to decent human society, and are exterminated – snared in traps, or torn apart by dogs. But not on the Dial. Here you are free to live, to run around, to fill your little faces with food. My one comfort is that you do not breed.”

Sensing that now was not the time to interrupt, the Traitor stayed silent as Mr Pitt turned away from the window, stalked over to one of the filing cabinets and selected a bulging brown file from the top drawer. He flicked through the pages, a look of disgust on his face.

“I’ve been looking over your case,” he said, “and you are without doubt one of slipperiest specimens I’ve had the misfortune to come across. You’d sell out your own mother for a handful of loose change. Ordinarily, I’d take great delight in making you suffer here for a few centuries, but you have been fortunate enough to catch me at a time when I have lost patience with this entire process.” Mr Pitt snapped the folder shut. “In short: I am willing to offer you a deal.”

The Traitor tried not to look surprised. “What kind of deal?”

“I’ve know how the rats pass their time here,” Mr Pitt replied. “Sniffing around nooks and crannies looking for a way out, burrowing little tunnels underground. Praying that one day they’ll be able to get back through the warp-hole to their homes. I know that the Tally-Ho are planning something big – I want you to tell me how, and when, they’re looking to make a run for it. Is that information you could obtain for me?”

The Traitor nodded slowly. “There’s usually someone who’ll talk – as long as you know the right way to ask them. But it’s risky. Ever since Luca betrayed them, the Tally-Ho have been on the lookout for anyone who might be a rat. If they catch me, I’ll be in big trouble.”

“If they catch you, the Tally-Ho will be the least of your problems,” Mr Pitt retorted. “You make a deal with me, you better hold up your end of the bargain.”

“I’ll do everything I can, sir, believe me. And if I succeed. . .?”

Mr Pitt opened a carved wooden box on his desk and pulled out a hand-rolled cigarette. Striking up a match, he lit the cigarette in his mouth, then held the wavering match near the Traitor’s folder.

“Records can be made to vanish,” he said. “Prisoners can disappear. Unless, of course, you’re happy to spend the next five hundred years here?”

Mr Pitt extinguished the match with a sharp flick of his wrist, and jabbed the blackened stub at the Traitor.

“You understand that no one can know about this? If anyone gets so much of a sniff of this conversation, it will be very bad news for you. A single loose word, and I will have a long time to make you regret it. Do I make myself clear?”

“Absolutely,” replied the Traitor, with the faintest trace of a smile. “You can trust me.”