Mist spilled out and curled around their ankles as the door to the red room dropped shut. It was dark out here, but warmer – anywhere would be warmer – and there was a soft tinkling sound, as of sand running through an hourglass.

For a while, they stood still in the dark, wondering what fresh horror was going to drop down on them. Jack was still holding his cheek where his mother had spat on it.

He was reeling, but not despairing. He didn't have the energy to despair. He expected Sita to lead him, but was shocked to feel her stumbling against him within a few paces of the door. She seemed to be weakening as she grew solid, as though she was gradually turning into that bruise-dark body he had seen lying in the gryphon's nest.

He supposed it meant they were winning. She was joining up with her body as they progressed through the gauntlet, ready to walk out of here a living girl. But there were so many perils attendant on being a living girl that it made him grit his teeth. Was this part of the test? Was this the Queen again, reminding him how terrified he would be if he ever managed to get what he wanted?

There was no time to dwell on it. Sita reached up for his arm and hissed, "Which way should we go?" 

And then the darkness splintered – everything splintered – as though they were trapped inside a kaleidoscope. Light shivered and bounced off every surface like a thousand fragments of glass. And, after the dimness of the last two rooms, it felt like glass, grazing their eyeballs on its mad trajectory through the room.

Jack reached for the axe at his back, assuming the light meant another monster to be fought, but this only made the sparkles fiercer. 

It was a long time before he realized that the shower of light was coming from the axe's blade. It was as though sunlight was catching the metal and being reflected back, except there was no sun, or any visible source of light except the axe itself.

Jack thought of all the years it had spent on the wall of the jigsaw room, under the skylights. Had it been storing light? Elsie had said it was a magical tool. It had seemed reassuringly un-magical up till now, but he supposed light was what they needed. It would have been churlish to complain.

And it meant they could now see their surroundings. They were in an underground corridor paved with black sand, which was radiant under the axe's light, yielding up all its constituent colours, like a meadow-full of flowers eager to be pollinated.

And then he noticed cracks in the brilliant carpet – channels where the sand was pouring away, hollows where it sagged as if the rock beneath it were subsiding. And a sound that he felt in his bones before he heard it in his ears: a deep, rumbling, cavernous sort of sound, like that of a mountain laughing.

"Do you think it's safe?" said Sita.

Jack started to say that he didn't, and received a mouthful of sand. It fountained up in front of them, causing them both to step back with their arms raised to shield their eyes. 

At first, he thought it was some kind of creature, erupting out of the sand to attack them. But it was rock. A column of rock with newly-torn edges, pouring sand as it rose. And, as it did so, their own patch of ground lurched sideways and tried to tip them off. The earth was breaking up beneath their feet, and they had to pick a direction to run in before they were buried.

Jack grabbed Sita with one arm and swung the axe with the other. It bit into the stone on the side of the rising column, and they followed in its wake, clinging to the handle as the rock propelled them upwards. He didn't know which way to go, but in a choice between down and up, he was damn-well choosing up.

They dangled from the axe's handle for one hideous moment, as the ground fell away from their feet. The column was still leaking sand, which poured over their hair, and got into their mouths and noses. 

Jack sought for footholds in the vertical rock. As soon as he'd found one, he launched himself up into the spray of sand, and found the edge of the top of the column. With Sita still dangling painfully from one arm, he shook the axe loose and swung it up again, burying it in the column's top, and hauling with all his might, until they were spread-eagled and coughing on a reasonably flat surface.

He didn't stop to catch his breath. He saw the ceiling approaching at speed, jagged with stalactites. He rolled over, pulled Sita to her feet, ran across the column, and leapt through a waterfall of sand onto a ledge, just before the rock and sand locked together with a crunch.

They dangled again, hauled themselves up again, used the axe to bite their way up an almost-vertical slope. Every time they thought they'd found a square-foot of stability, it lurched underneath them, sending them off into the torrent of sand. 

He couldn't believe this was part of the gauntlet. He couldn't believe this was localized. The Queen's realm was breaking up under their feet, and all bets appeared to be off.

Finally, they found a slope leading upwards, a valley running and seething with black sand. Sita was dangling helplessly from his arm by this point. Her legs had given out. Jack hauled her onto his back and risked a mouthful – a throatful – of sand telling her to hang on. He didn't know whether she heard, or whether it was just instinct, but she locked her hands round his neck and clung on as he ran forwards.

More sand was bearing down on them now. They went from wading to swimming in it, using the axe to bite into anything solid that came their way. He heard Sita coughing, and then suddenly she wasn't coughing. Her weight lessened on his back, as if every muscle of her body had quite suddenly relaxed. Her hands slipped from his neck, and he threw the axe away from him, twisted in mid-air, grabbed her with both hands and prepared to tumble with her into whatever awful void the sand was running to. He took a deep breath, and let the stuff close over his head.

But it wasn't dark, even under the sand. There was no air to breathe, no room to manoeuvre, but there was a faint, muffled glow ahead of him, working its way between the grains of sand. He couldn't have said how he knew, but he knew it was the axe. It must have stuck somewhere when he'd thrown it, and was now juddering in the rock, sending out its light like a beacon.

Jack kicked out with his legs and lurched towards it, still clutching Sita with both hands. They were being swept away so fast that he had to fight the current to reach it, and he knew that if he tried to breathe, the sand would pour into his throat and weigh him down. 

He swam upstream with that one breath burning in his lungs and his eyes so full of sand that he couldn't tell the axe's light from the swamping redness in his vision. But he found it – or it found him. Jack clung onto the handle, clamping Sita against the valley wall with the weight of his body, and drew himself up.

There was a breath – perhaps two – and a blessedly flat piece of rock to collapse on. He wasn't sure if he'd let go of the axe, but he definitely had Sita. She was a dead weight on top of him. And, though he couldn't see anything through the sand in his eyes, he positioned a hand on her back and waited, heart thudding, until the motion of her breathing made it rise, before he passed out.

***

He woke up terrified, because somewhere a door was closing against them, and he didn't know how long he'd been asleep.

He also felt desiccated. There was grit under his nails and in his nostrils, and someone seemed to have been at work with sandpaper at the back of his throat. His eyelids rasped and scraped against his eyeballs when he blinked.

Now that the sand-slide had settled down, he was beginning to think this might all have been part of the gauntlet, rather than a natural catastrophe. Every other room had been apocalyptically dreadful, in its own way. This had just been more direct.

Which meant that, somewhere, the clock was still ticking. In fact, he felt as though he'd been inside the hourglass that measured his allotted time in this place. He'd been sucked under, squeezed through the point where the glass was narrowest, and tumbled down with the rest of the sand. Now there was just a light trickle on his head telling him his time had almost expired. When it stopped, he'd be buried – or, worse still, compelled to go through the whole process again when the hourglass was turned over.

He opened his eyes again and realized that the axe was buried in the wall of rock at his elbow, its handle still juddering with the force that had driven it in. He couldn't have been unconscious for long if the axe was still juddering, could he?

He shook Sita, and she groaned and squirmed away as if he was trying to wake her up for school on a cold morning. His dry lips cracked into a smile. "Time to get up."

"Not until the earth stops falling."

"It has. I think."

They were in a vast cavern – too big for echoes, even. He couldn't make out the cave-ceiling above him. There was an orange glow on the horizon which looked a bit like sunrise, but was probably an erupting volcano getting ready to scorch them.

Sita unpinned her braids and shook sand out of her hair. There was a bruise taking up most of her right cheek now. It had only been an outline before. "Where's the door?" she said, getting to her feet and wincing as she put her weight on her injured leg.

Jack tried to listen for the grinding sound, but could only hear the shift and trickle of sand. The door could have been buried a hundred feet beneath them. They might have to dive through the maelstrom they'd only just escaped to reach it now.

He prised the axe out of the rock-face and held it up, letting its beam scythe through the darkness ahead. To their left, the sands sloped upwards, and something was reflecting the light back at them. Water, perhaps? A river or lake? It might feed into the waterfall that thundered down Vassago's canyon. And, on the basis that they had started somewhere near there, and the Queen was far too languorous to move around, he decided they ought to head in that direction.

The orange glow on top of the mountains was an eruption. It got brighter as they walked, in mockery of sunrise, but it was too distant to be a threat. Anyway, he had seen erupting volcanoes in the distance at Vassago's canyon, hadn't he? 

And now here was a lake: black and placid and ruddy with the lava-glow. The mountains cupped it in a kind of curve – no, a circle, he added, glancing to his right and seeing that there was another curve of peaks in that direction. They formed a protective ring round the black lake, as if they were guarding it from something.

They had to be close. Jack quickened his pace and tried to nudge Sita onwards. She was wincing with every step.

It was a few minutes before they heard the grinding sound, and another few before they saw the door. The space underneath it was a thin, silvery line in the darkness ahead – perhaps big enough to roll underneath, but not for very much longer.

He seized Sita by the elbow and half-supported, half-carried her over the sands. For a while, he had eyes for nothing except the door, but his mind was working treacherously in the background, joining up the details he'd already noticed.

A black lake, surrounded by a circlet of mountains. A furnace-like light that had stained their faces red back on the Academy's lawns.

"Wait a minute," he said, skidding to a halt in the sand.

"What?"

"Wait a minute."

"We don't have a minute!" Sita protested, trying to drag him forwards on legs that barely worked.

"I know this place..."

The lake was huge and god knew how deep. It could take him a hundred years to sift through every square foot, and the gap at the bottom of the door was barely passable now.

Still, he staggered up to the shore and splashed a few paces into the dark water. It wasn't transparent. Now that he came to stand in it, he wasn't completely sure that it was water. He wouldn't be able to see an inch in front of his face down there.

But the axe dipped in his hand and touched the surface, as if impatient to carve a way through. He wasn't sure if he had made it do that or if it was moving of its own accord.

"What are you doing?" Sita shouted.

Jack whipped round urgently. "Let me try this – just let me try. Thirty seconds, Sita."

"We haven't even got ten!" she wailed.

"Ten, then," he said, raising a hand to pacify her. "Five." 

He plunged his other arm into the water, as if he was expecting the ring to fly into his hand. He couldn't take his eyes off the patterns of light on the water's surface – the way they coalesced and broke apart like the stars on Elsie's skin.

"If I can only have you or happiness, then of course I'll choose you," he babbled. "But if I could have both..."

He plunged another hand in, raked the pebbles at the edge of the shore, felt the water trickle through his fingers, completely devoid of rings.

Some part of his mind was screaming at him to be sensible. Gold didn't float. The chances of just happening upon the thing he wanted were a million to one, and Sita needed help – she needed Sergei – she needed medicine and food and warm blankets.

"Ishmael," she said quietly. "Jack. We're so close. After all this..."

Jack shook his head, half-laughing. He wanted to tell her that it was because they'd been through all this – and somehow, against the odds, managed to survive – that he was sure the ring was here, just out of reach of his fingers, just one more grasp away. 

This was serendipity. It was meant to happen. How could fate have brought him here without meaning him to get the ring? Wouldn't it be the cruellest thing in the world to dangle this chance before him and not let him-?

Oh. Yes. It would. It would be as cruel as making him kick Ellini in the head, or walk down a corridor lined with all the men he'd killed. As cruel as making his mother spit at him. That kind of cruel.

Jack grabbed Sita round the waist and ran with her, his throat burning with anger and horror and shame. He blinked hard tears out of his eyes and sprinted without drawing breath, screwed up every muscle of his body into a desperate dash through the sand.

Please please please please please, he thought. I was stupid, but just for a moment. Don't make that moment count. Don't make Sita suffer it.

He threw her under the doorway first and then wedged the axe against the stone, blade upwards, to try and keep it open. It shivered with the weight – it even started to slice – but it slowed the door for the two seconds he needed to squeeze under the gap. 

He risked severing his arm to pull it out again, but that seemed like the least he could do. It came free in a burst of sparks, and Jack felt the thud shudder through his entire body as the door hit the ground beside him. He took a few shaky, sickening seconds to be sure that all his limbs were on the right side of the door, and then he let his head drop.