Raynz had thought of everything. Even now, with terror rising through him like ice water, Ambrose could appreciate the way he'd been outmanoeuvred.

He'd never been all that interested in chess back at the School, but the two of them had played a handful of times and always attracted a crowd of onlookers. Perhaps the novelty had been the disparity in their ages and stations; Raynz had been one annual from his Masterwork, while Ambrose was a mere fledgling, eight years his junior. They made their moves rapidly, their eyes fixed on the board, the pieces tapping out staccato rhythms as one displaced another.

Astronomer moves to the third rank, fifth file, and blocks an Alchemist. Fortress grinds a zigzag path, crushing two Munchkin Envoys in its wake. Lion to Queen's defence, driven back by an enemy Elephant, which finds itself suddenly immobilised in a net of fatal choices.

Sometimes Ambrose won, and then Raynz would grin widely, offering a handshake that always lasted a little too long, while friends would clap the older scientist on the back, praising his sportsmanship. Even then, Ambrose knew that wasn't his real smile. If you paid attention, you could see each muscle being recruited, woken to an arduous and unwelcome duty.

If you wanted to see Raynz's true smile, you had to wait until he was on the cusp of victory. Then, it would emerge, subtle as a night-creeping animal, treacherous as a thin scrim of ice on a deep, still pond. It lit his eyes in a way merriment shouldn't. Once or twice, it had alerted Ambrose to danger, and he had struck out with an unexpected sacrifice, sending the game careering down a different path. But usually, by the time you saw it, it was already too late.

Like now.

They'd hurt him, but carefully – if such a thing were possible. They'd found nothing in his workroom at the City; his blueprints were drifting ash, and their contents survived only in the landscape of his mind, so his survival was important to the Sorceress for the time being. The beatings had been clinical, the administrations of electricity calculated to tolerable limits.

When Raynz saw he was getting nowhere, he'd changed tack. His 'surgical interrogation' experiments had flourished with Azkadelia's approval, and he wasted no further time in showing Ambrose his future, should he fail to co-operate.

That had been a horror, but it wasn't going to happen to him. It couldn't. The contents of his mind was his world, his universe. Raynz couldn't be allowed to take it and pin it like a butterfly on a board, exposed and exploitable. Too many secrets. Too many things he could twist into weapons.

The Mystic Man had shown him ways. Meditations and mathematical mandalas, sequences of calculation that branched and spread like vines, self-generating paradoxes. It would take hours, and it would be a wrench to leave the world behind – full of wonder as it was, even now – but he would isolate himself in the eye of an impenetrable mindstorm and let it scour his neural pathways until nothing was left for Raynz to find but a shredded almanac, obsolete, pointing to nothing. Ambrose had waited only as long as it took for the Longcoats to take the pitiful Headcase away, and then began to shut himself down.

Astronomer moves diagonally to the eighth file, evading conversion, and the Queen remains in sight.

Raynz had other plans. He must have broken through the protective cordon of Tin Men, or perhaps he'd had eyes in the Mystic Man's Central City residence much earlier than anyone had suspected. Azkadelia's spies had already learned enough to build the tower, even without the complex machinery it would house. Either way, he knew enough to keep Ambrose from his scheme. Instead of a cell, a new room was found, higher in the Sunseeder's imposing bulk. Closer to Raynz. Closer to the sound of his work.

A phalanx of Tin Men cut down. The board shudders. Strategy is caught up in a whirling wind that sounds like screams, the drill, the bone saw. Reason scatters.

No sleep. No peace. No way to concentrate.

From the narrow, unglazed window, more a vent then a viewpoint, Ambrose watched Longcoats marching, supply trucks of grey-green metal beetling in and out of the compound. A larger vehicle arrived, disgorging prisoners in a sullen line. One stumbled, and another – taking advantage of the guard's distraction – broke away and made for the front of the vehicle, perhaps hoping to commandeer it. A gunshot tumbled him into the dust, the sound curt and unimportant, like a book being snapped shut in another room.

They didn't even tell him to stop.

Sorrow washed over him, huge and sudden and... absurd. The man was a stranger. The Sorceress had emptied the School of Science. Friends had vanished in the night, perhaps fled, perhaps something worse. There didn't seem to be time enough to mourn all those missing faces, but this one man's death struck him breathless with grief.

He's all of them. Leo with her botanical creations, and her tireless attempts to bond with the Papay-Walkers. Professor Vox, who was in the middle of a lecture on 'The Semiotics of Pulse Communication' when they dragged him out as a traitor against the New Order. Copeland and Ervic, the Tin Men who guarded my laboratory.

DG...

Little DG, who never hurt anyone at all.

Anger was better than despair. It couldn't take the shackles from his wrists, but it got him to his feet. The Longcoats checked on him every half-hour, rousing him if he seemed likely to sleep. Black-swathed, harsh and raucous, they plagued him like crows, pecking and pulling, leaving him tattered.

Enough.

There was the chair, too flimsy to be a weapon. There was his discarded uniform coat, torn where they'd ripped Queen Iskra's insignia from his shoulders, a loop of brocade hanging like a noose.

It wouldn't be strong enough. Even if I braided it. He might be able to tear strips of cloth from the coat itself, tie them together. Then tie them to what? There's nothing in here. Besides, they'd be back soon. Cackling. Taunting.

Like crows...

It took no strength to break the chair, which was fortunate. The splintered spars came free from the back easily, rattling on the floor like bones. A chair leg to support the shoulders, a shorter length of wood to brace the neck. Braid to join the two, and then wedge the short spar into the window slot. A poor scarecrow, but maybe it would serve?

The first Longcoat to go through the door saw a figure at the window, slumped into the gap as though caught. The second saw his comrade fly sideways, propelled by a kick that would have snapped his neck at full power.

Lured by a decoy, the enemy finds himself on a poisoned square, and the attack is swift, if not devastating. Bringing his chained hands down on the second Longcoat's head, Ambrose was momentarily gratified to see that it was Kinley, the least pleasant of his gaolers.

Now to run. But where?

There was down, if he could evade the Longcoats, down to possible freedom through the exhaust tunnels and cold, echoing darkness haunted by the howls of Viewers in their cells. There was up, which could lead to only one conclusion. It wasn't really much of a choice at all.

One flight of stairs, and the alarm was raised. Amplified voices gave meaningless commands, shouts, a gunshot. It didn't matter. None of it mattered. He knew these passages, these turns and alcoves like the inside of his own mind. You'd hunt me through my own invention? Come on, then!

Pain was forgotten. Exhaustion was forgotten. He rode on a wave of adrenaline, and the certainty of an equation solved beyond doubt. Another level gone, and he slammed the door on a group of startled technicians, vaulting a bank of dials. Service access – a metal ladder and one Longcoat who was already folding up before he knew what had hit him.

Nothing left to play but the endgame.

One more doorway. One more half-finished cry of surprised dismay, curtailed by a righteous kick to the jaw. The sounds of pursuit were louder, but it didn't matter because –

Sunslight. Had it ever felt this kind, this welcoming, before? He crossed the circle of the pulse array, the dark glass bursting with rainbows as the light hit complex dichroic filters.

And the sky was a bowl of endless blue.

And the soft breeze cut cleanly through smoke and seared metal.

And oh, the world was beautiful... and such a very long way down.

'Wait!'

He did. He had to, if only for one last exhilarating taste of the air, the touch of warmth on his skin. Turning cautiously on the balustrade, his hands in front of him for balance, he watched Raynz emerge from the tower, the Sorceress behind him. Longcoats boiled out onto the balcony in a commotion of boots and ratcheting guns.

'Don't be foolish, Ambrose. Come down and let's work something out.' Raynz looked unhealthy in the daylight – his skin dull and vaguely yellow, like a candle left too long on a dusty windowsill.

Ambrose shook his head. 'It's a little late to start asking nicely.'

Azkadelia swept forward, her own hands outstretched as if to take his. 'You could still be an advisor. My advisor. Think how you could help bring this divided land together. Think how you could serve your queen.'

'I am.' He sighed, only faintly regretful, and let himself fall back into empty air.

There was a painless moment, the chill and rush of acceleration...

...then fingers clawed at him, curling into his clothes, his hair, his flesh. Shrieking, snub-nosed Mobats caught him up, a dirty, leathery cloud of wings buffeting him as he fought, some separate, inexorable part of his mind graphing the trajectory of his fall. The curve, robbed of its conclusion, cheating the Y-axis.

They dropped him on the flagstones at Azkadelia's feet. He spread his fingers against the stone, seeking its warmth, its strength. Umaii watch over me, protect me. Gewen, keep me in the hollow of your hand.

'Raynz?'

'At once, my queen. You – take the prisoner to my laboratory. We'll operate immediately.'

Ambrose tried not to look up when they dragged him past Raynz. He didn't want to see the smile he knew would be there.

Not that it mattered – by the time you saw it, it was already too late.