The guard creatures were growing agitated, thought Duffy.

  They were shuffling back and forth in their positions around the humming, vibrating Furnace and several had clawed tentacles extended, waving them around as if they expected to come under attack at any moment. They seemed nervous, if it were possible to ascribe human emotions to such alien creatures, but nervous of what?

  "What's gotten into them?" he muttered to himself, looking briefly up from the feverish mathematician. Rahul was getting worse, though, and his attention was quickly dragged back to the livid, pus-ridden wounds. He dipped his cloth in the bowl of water again and dampened his bare chest in an attempt to keep him cool. It was the only thing he could think to do until Sarah got back with the medicine.

  "Why don't you ask them?" asked Bergman, turning away from the image of the alien world to look at him. "They speak our language now."

  "Yes, I saw you talking to them a while back. Quite a furtive conversation you were having. What were you saying that you didn't want anyone anyone else to overhear?"

  Bergman just gestured to the creatures again, smiling enigmatically.

  Why not? thought Duffy. "Hey, you," he called across to the nearest creature. "What's going on?"

  He hadn't really expected an answer, and so he was surprised when the creature turned one of its flower-heads to look at him. "Duffy close doors," it said in its chalk-on-a-blackboard voice. It pointed towards the doors up to the car park with a clawed tentacle. Designating an object by pointing to it was a form of non-verbal communication they'd learned only the day before.

  "What?" said the physicist in surprise.

  "Duffy close doors," the creature repeated. "Now."

  "Why?"

  "Duffy must not die. Duffy will die if doors are not closed."

  "Better do what it says," said Bergman. "They wouldn't want to us to do it unless they had a good reason." He headed towards the doors and beckoned the other man to follow.

  "Be fast," said the guard creature. "There is little time."

  Duffy stood up and walked up the ramp to where Bergman was waiting. The creatures guarding the wagon turned their flower-heads to look at him as he approached but otherwise made no reaction. The sun was directly overhead now and the day was reaching its full heat. He felt it on his bare arms as he stepped out into the car park. A heat that told him his pale skin would start to burn in just an hour or so if he remained exposed to it.

  He paused for a moment and looked down the street. There was some kind of dust down there, drifting in the wind. Probably another building had collapsed. Sentry plants turned their eyes to look at him and the strange gourds hanging from the trees seemed to pulse with a horrid kind of life, as if they were about to discharge swarms of vicious hornets. They scared him in a way he couldn't explain, and closing the doors suddenly seemed like a good idea just to block the sight of them. Somewhere in the distance he thought he could hear car engines. Probably just a hallucination, he thought. He was probably right on the edge of the area protected by the magnetic field of the Furnace.

  The doors were heavy, but with Bergman's help he was able to lift one, raise it to vertical and then drop it down with a loud bang to half-block the opening down to the basement. "How do we get back down there?" he asked as they lifted the other door.

  "Through the main entrance to the building," Bergman replied. "But we'll have to be fast. I don't like the look of that dust."

  "You think it's toxic?"

  "You want to breathe it and find out?"

  Good point. They closed the other door and then ran across the car park to where the main entrance to the building had once been, before the glass that had fronted the whole building had shattered under its own weight. Bergman was wearing a magnet, he saw. The man hadn't left the basement once since the expedition had arrived. One of the creatures must have brought it to him. He wondered why they would do that. Wouldn't they rather have another anomaly creature emerge from his corpse?

  He winced with pain as one of the sharp crystals growing on the ground sliced clean through the sole of his shoe and into his foot. "Dammit!"

  "Keep moving," Bergman called back to him. "The dust is almost here."

  "Why would they release toxic dust now?" asked Duffy as he limped on. "Sarah's still out there."

  "I can only guess," Bergman replied. "Maybe there's another expedition approaching."

  "Another expedition?"

  "You didn't think they'd try again? Probably a fully military expedition this time with just one objective; to destroy the Furnace. Didn't you hear the car engines?"

  Duffy stared in surprise. "That was real?"

  "Probably. I'm guessing the dust is some kind of biological agent, designed to kill anything that breathes it. That's why they wanted us to close the doors. They want us to live."

  "They want you to live you mean," said the other physicist as they reached the entrance. They went in, their feet crunching on the piles of broken glass, and set off along the corridor towards the basement. "Because you're mad. You want them to take over the whole world, even if it means the end of the human race."

  "The human race doesn't matter. Beauty matters. What you call the anomaly will transform the world. Make it beautiful."

  "What does beauty matter of there's no-one left to see it?"

  You might be reading a stolen copy. Visit Royal Road for the authentic version.

  "The crystal entity will see it. And you're wrong. It's not just me they want to survive. They want you to live too. Duffy must not die. That's what they said. Remember?"

  Duffy stared at the back of his head as the other man preceded him along the corridor. "So why do they want me to live?"

  "Because you're the Plan B. I'm guessing the military will have sent enough men and firepower to get past whatever obstacles the creatures put in their way. The creatures probably won't be able to stop them from destroying the Furnace. If they do, the Crystal Entity will be relying on you to build a new one."

  Duffy laughed. "In its dreams," he said.

  "That's why I've been teaching you everything I know about knot theory. About how the Furnace works. Didn't you wonder why I was doing that?"

  "Egotism. You wanted me to see how clever you were."

  Bergman laughed. "I taught you all about the Furnace so that you could build another one one day."

  "Which I'm obviously never going to do. I've seen what this device of yours does now. I'll forget everything you told me and devote myself to another area of physics. I'll make sure no-one ever follows your research."

  They arrived back at the stairs that led down to the basement. Duffy hurried down and went to check up on Rahul. The mathematician was still in pain but seemed no worse. He knelt down beside him, dipped the cloth in the water and resumed wiping down his body.

  "You were never really interested in geology, were you?" said Bergman, standing idly a short distance to the side.

  "What?" said Duffy, not really listening.

  "I told you that I went through to that other world. I couldn't stay long. Just a minute or so. The air's not breathable over there and that's the longest I could hold my breath. It was long enough to pick up a few rocks and crystals, though, and bring them back. I showed them to you, on the table over there. Next to my computer."

  "Everyone needs a hobby," said Duffy distractedly. "One of my cousins collects stamps."

  "Those rocks are a good deal more valuable than stamps. Back in the first day after the anomaly appeared, before they sealed off the city, I sent one of them to Professor Chen Yan, along with a complete copy of my computer's hard drive. Everything he needs to know to build a Furnace of his own. I lied when I said you were Plan B, Professor Duffy. You're Plan C. Professor Yan is Plan B."

  "Ernst," said Duffy. "The anomaly had been in the news for weeks. The whole world knows what's happened here. Nobody's going to risk building another Furnace, no matter if you've found diamonds or whatever on that other world."

  "Not diamonds, Professor. Not any kind of gemstone known on this world. Something far more valuable. Something so valuable that, once it becomes known, every government in the world is going to be clamouring for it. If Chen Yan's told the Chinese government what I sent him they're probably already building a Furnace of their own. They'll build safeguards into it, of course, so they can shut it down from a safe distance any time they want. It doesn't matter. The Crystal Entity will find a way to turn things to its advantage. The world will be transformed and made beautiful. And if the Chinese don't, the Americans will. I sent them the same information I sent Professor Yan, along with a rock to go with it. They'll persuade you to build another Furnace, in a more convenient location. Away from major cities and with an off switch they can flip from Washington."

  There was such certainty in the man's voice that Duffy turned and looked at him. "So what are these rocks?" he asked. "What could possibly be so valuable?"

  "There's a bunch of them still sitting on the table, just over there," said Bergman with a smile. "Why not go and take a look at them?"

  Duffy stared at him, then looked down at Rahul. He wasn't really doing anything for him, he realised. He was fooling himself, to make himself feel better. To make himself feel less guilty and helpless. He stood, therefore, and looked at Bergman, who smiled and nodded his head towards the table. Duffy looked at it, then walked across to it.

  The stones were unremarkable at first glance. One looked like a piece of broken quartz. Another had streaks of red and green going through it. He picked it up to look at it more closely, but nothing else revealed itself. He put it back down and reached for another.

  Out of the corner of his eye he saw Bergman lean forward eagerly as his hand approached the third rock. That was the one. The special rock of great value that Bergman thought would tempt the world into creating another Furnace. It was a very pale shade of green. Almost white, with specks of darker green scattered through it. "It's not radioactive is it?" he asked, snatching his hand back as the thought came to him.

  "So far as I know it's completely safe to touch," Bergman replied.

  Duffy stared at him, trying to spot any trace of deception on his face, but there was only eagerness as Bergman waited for him to discover its value for himself. Duffy found himself growing curious. Bergman was a highly intelligent man. Probably one of the smartest men on Earth. If he thought it was as valuable as he said then it probably was, but why? Duffy reached out, took the rock between his fingers and lifted it...

  Or tried to. It was difficult to lift. Not because it was heavy but as if it was sitting in a bowl of viscous syrup that was hard to move it through. There was no syrup, though. Just empty air. Jeffcott looked across at Bergman, who was grinning wider as he waited to Duffy to see the truth. Duffy looked back at the rock and tried to move it again. It was easier to move in some directions than others, he found. It moved up and down almost without resistance but it required almost all his strength to move it forward and back, or left and right. What the hell was going on?

  Okay, he thought. Think about this rationally. What's so special about up and down? Well, it was towards and away from the centre of the Earth, of course. Could it be comething to do with gravity? But he would have expected that to make it easier to move it up than down or vice versa. In contrast, moving up and down were equally effortless, as if it were just an ordinary lump of rock.

  Okay, so turn it around. What's special about left and right, and forward and back? Well, they were parallel to the surface of the Earth. Also, they were cutting across the lines of magnetic force being generated by the Furnace...

  He felt his heart being gripped by a fist of ice and turned to see Bergman almost capering with glee. "You see?" he laughed. "You see?"

  "It's flux-pinning the Furnace's magnetic field," said Duffy breathlessly. His pulse was racing, he realised, as if he'd just run a mile.

  "Yes!" cried Bergman in jubilation. "Yes!"

  Duffy stared back down at the ordinary-looking rock he was holding in his hand. All of a sudden he knew that everything Bergman had said was true. There was no government in the world that would be able to resist the temptation this rock represented. There was nothing they wouldn't do to get hold of it, no matter the danger to the world. They would lust after the riches, the power it would give them. The ability to generate and transmit power in unlimited quantities. The ability to create weapons of unimaginable violence. The country that gained a monopoly on this stuff would rule the world. Even the military might of the United States would be helpless against a country that obtained an unlimited supply of this substance.

  His hand was growing sweaty as he held the rock. His whole mind was filled with the knowledge that his mortal hand was holding the dream substance that scientists all across the world had been searching for decades. The fact that he was Canadian would mean nothing to the Americans, he knew. They would never let him go home, and they would use every bribe, every threat, to make him build another Furnace. He could hold out for a time, but he knew that eventually he would give in. There were psychological techniques they would use against him to make him glad to do it. The world was as good as doomed, and it would be because of him.

  He looked across at Bergman again, and was terrified by the happiness he saw there. The other man was staring at the image of the other world again, dreaming of the day when the Earth was transformed to be just like it. Mankind extinct because if its desire for the rock he was still holding.

  The room-temperature superconductor.