"...we're not sure if particle incursions represent a driving force behind multiverse evolution. It's possible that these random events, when added to a universe, force laws of physics to adapt. It's plausible that over time our universe has gained its laws of physics from such incursions. Generally we know these incursions cause new laws to be produced and ultimately it's the stable, ubiquitous laws of physics which are healthy. Almost all those caused by particle incursions are not..." –extract from J. Kriegskorte at a question and answer panel, Fifth interdisciplinary conference of Macroevolutionary dynamics.

A couple of hours earlier in the past Matt and Scott jogged past the Serpentine art gallery on the return leg back home. It wasn't far now. Agent Raynes was still sleeping lightly in business class with one eye occasionally opening to check the situation. The fifth floor of the bookstore was playing light classical music. Jazz would start in an hour. All was calm.

Such a brief expedition back into the past should not be worried about thanks to Einstein's theories of relativity, and other quirks of profoundly strange science. Kudos to him. The trick to it as always is to make space and time quarrel hard enough that they don't notice you, hungry with the power of an entire roaring star and black holes in hand, burning down their house and pissing on their fully-theoretical rosebushes. That's the thing about relativity. Take any relatives you have and lock them in a social science laboratory for long enough and your great aunt will inevitably quarrel enough to throw a right hook at you. Now do that at a bigger level to space itself.

Since space and time are very closely related indeed and live under cramped living conditions, you might find under black-hole induced moments that the stress leads to incestuous space-time passion. Moving backwards you might see some unholy relative conditions (assuming you can see any light at all, which you can't). The downside of this is violent fighting between time and space and a break-down of reality. The upside being that Matt and Scott are now still on their jog, much to their displeasure and Raynes is yet to get a phone call. So while time shouts that 'space, you fat chunk of lard, you could lose a few gigatonnes of dark matter' and space replies with something weak like 'I'm not the one always fuckin' late' it's okay to sneak by in fits of nerd-induced froth.

"I'm telling you M, they're divas. I swear they'll cross your path on purpose. They wait for you to try."

"You're paranoid," gasped Matt.

"This guy honest to God almost rams me with six-hundred pounds of mincemeat. Bent the frame and the chain slipped."

"Dude, they're police horses though."

"And brand new tyres are chugging manure at this point." It was going well. The athlete had been red in the face a good while. Sweat drizzled down his chin. Both had been panting as they passed Speaker's Corner. Scott blamed horses for a lot more social problems than Matt thought possible.

"You throw Black Beauty under the bus for everything."

"Bus wouldn't survive the impact. Those horseshoes fly like shurikens. Decapitate a driver at sixty paces."

"You're awful," said Matt.

"I'm a realist. God agrees with me. It's horsemen of the apocalypse for a reason."

They'd rounded the Northern Unicorn and stood under its glare a little while back, and now this was the final stretch. Breathing was a hot pain now. Matt had hit a rhythm, a painful one but still, a rhythm. And Scott was throwing him off. God, he had another essay to write when he got home. The last one had been on flatfish, and Matt now ordered them at every opportunity. No restaurant, be it French, Italian or any other was safe from post-mortem revenge on those fish for making him write that essay. He sneezed.

"God. Ow."

"That's exactly what I'm talking about, M. Horse-induced hay-fever. If there wasn't any hay you'd be fine."

"Not how hay fever works but okay."

"You sure about that?"

"I'm gonna collapse Scott. Next bridge?"

"Sure."

He could see it. There were a few more turns, the car park on one side and the gallery to go before the bridge.

"Have you ever seen frieze art?" Scott stared with some apprehension at the Serpentine gallery, solitary home of bizarre.

"No."

"I don't get it. They take like a cube made of plastic or I dunno, like a three foot high letter 'T'..."

"Why that letter and not others?" Matt grimaced, suppressed another sneeze.

"Look, it doesn't matter. Whatever. Any letter, so long as whatever it is looks like an everyday object, or semi-normal. It's supposed to make you think. It's like art, but weirder."

"Right." The Serpentine gallery fell behind. Just a few more seconds. Just a bit more and he could rest.

"Right, so someone spends three months perfecting the hell out of that letter. Typeface, modelling plastic, everything."

"I guess if they like it?"

"And then they give a public exhibition. And most people just go 'huh' and move on."

"How are you not out of breath?"

"You need to do better, M. One of these days we're gonna have a proper conversation on these runs."

Scott gave up. There were a few landmarks left – the real Serpentine Bridge with its second duck stop. Beyond it there was the great statue of Prince Albert sitting gold on his plinth that you'd half-salute from a distance as you left the park. And above it all the rich blue sky heaved to staple the ground from built-up horizon to horizon in an unnerving rarity for London. Scott approached the bridge with its backdrop of heavy roadworks signs and metal poles. Construction work, steel fences and steamrollers littered the wayside, traffic piled up at the obstruction and in the distance on the far side a jackhammer roared into life at a decibel level close to gunfire. A new cycle path was coming to life for which Scott was grateful. He looked back and saw his friend stopped. He went back.

"What's up?"

"It's just gravel," said Matt. Asphalt ground together in his socks. He took off a shoe.

"M, get off me. This shirt is discount but still, don't pull me over." Scott was as good a support as any.

"Look I can't run like this, okay?"

"Run? You mean slow jog? Can't you just put your foot on the ground?" This probably never occurs to people.

Matt struggled and finally shook out the last of the irritants. Ahead a manhole cover vented steam in conspiratorial streaks.

"There you go, M, see?"

"What?"

"Like I said, it's like New York. Covers are hot because they're re-doing the water under here. Genius." Scott pointed to the roadworks.

But that wasn't true. And there were many urban myths. There were more urban myths than just the tunnels. There was the myths about what was down there in the tunnels, screaming and metallic and full of sensitive data. There'd be lecturers who'd go silent if they remembered that your meeting clashed with their responsibilities somewhere they couldn't say. They wouldn't tell you why your meeting was rescheduled. But they'd let you know they had to reschedule it. There was no choice.

And when the university tore down buildings they'd keep the sites closed. No engineering students would go look at the remnants as part of a field trip. They'd put up those big screens around the building works with smiling faces and quotes from past students, and throw up the cranes and the concrete mixers in what felt like record time. And you'd wonder why no-one would tell you what construction firm was working on the site.

And somewhere in those tunnels that ran beneath the university and Hyde park a physicist turned on her radio. A faint crackling told her she was now broadcasting at ungodly frequencies. She told her team what she needed. HAM radio enthusiasts for miles around would have choked if they'd known. There's a whole rainbow spectrum of colourful radio frequencies that might have had dozens asphyxiating and foaming at the mouth, including this one. She wished he could see them falling off their metal chairs backwards in garages across suburban London and spilling cold tea all over delicate radio machinery.

She sat in front of a stained desktop with the task windows and ancient graphs blazing in CRT glory. Her radio messages were never alone in suspicious frequencies. Ukrainian spies considered which concert to go to on a Friday evening and argued over prices within restricted megahertz. The occasional American diplomat too paranoid of the NSA to use a phone might be overheard talking of how he was certain he didn't have any offshore accounts, and a handful of military jets dared each other on how low each could fly somewhere north of Berkshire.

Instabilities in the universe are inevitable, so inevitable and variable in their effect that their presence could be harmless or devastating. You can be sure that by the time you've worked out there's been an instability in the laws of physics any way of stopping it is far back in the past, and no amount of twenty-first century maths can undo it. Constants might shift a little here and there under normal conditions. New laws may appear. Usually people throw out excuses that boil down to 'quantum physics, and we don't know why', or would in many cases if they knew about it. But sometimes the reason something happens isn't quantum physics. Sometimes it's just bad luck. There's no obvious rhyme or reason why any set of physical constants should be any certain value, why gravity really needs to be just so.

Not long remained.

The students relit their discussion on frieze art. Scott's opinion of certain artists left something to be desired. His friend was surprised Scott could even name some frieze artists and wasn't sure if it wasn't all just junk he'd made up. Matt stood a few feet from a manhole cover and stopped to recover for a few moments and to get ready for the last leg of the run. A duck by the waterside wandered a fair bit in the lush greening reeds of the Serpentine. It quacked but a jackhammer drowned it out and it ended up too far to be the one on which the anomaly would settle.

Thousands of hertz higher than the best guard dog's range a tinny whirring of transformers and super-cooling echoed through the deep pipework beneath them, and out through the grate. A series of detectors twenty feet wide waited down there in the depths.

A bank of magnets clicked into place. All was well. A young woman was about to get today's first set of results, and would run the machine for maybe an hour or two. Four years' research for a list of numbers and a weak line graph had been her life until this job. Countless delays, bad funding and after all her efforts and tears, a surprising rejection from the world's largest physics institute. Then help had come, and here she was here with stable employment. Underground, but with stable employment. She squinted behind rimless glasses.

Accelerating atoms almost imperceptibly completed their loop beneath the bridge. Something wholly unknown spontaneously completed an unstable loop on an entirely different scale. A computer timer hit full zeroes. Sheer determinism meant there was no way to avoid either event happening, or the experiment.

Atoms crackled against one another in an interaction that could be only described as 'normal', but at energy levels that allowed something completely not normal to happen too. Pity the detectors missed most of the action. Dr. Lana Peregrine looked up from her radio to watch the screen and fixed her glasses back in place.

The conditions could afterwards never have been repeated exactly, and even if they had it still might've never happened again. It would take a long time and a bit of help to even realize something odd had happened. The universe's defence mechanisms against the irrationality forced some fundamental changes, the world tried its best to maintain cause and effect. Something similar had happened before and the world had survived. The irrational effect cascaded into motion of its own accord and ballooned in magnitude. Several separate realities were infected with it, briefly bound together in a chaotic rhythm.

Something shimmered and rumbled. Matt felt a pressure on his chest. He blinked.

"M, you ready for a sprint down Exhibition Road to finish it off?" That was rich.

"Hmm? Scott, no, I can only take one a day mate. You won." The manhole cover had stopped venting anything. It was so quiet. He couldn't think.

"One a day? Haven't seen you sprint at all. Like hell you've done enough exercise. Come on. You've got breakfast and coffee to burn." Scott slapped him on the back. Matt pulled out his phone and noticed the screen was cracked.

"What? I haven't had breakfast, or coffee. My phon-" He held it up.

"Sure. Since when? You going all soft and caffeine-free like April?" Scott grinned.

He had a headache. He thought April loved her weird teas and hot drinks. She always drank them through exams with her rap playlist. He touched his forehead and felt for a bandage. He hadn't hit himself on anything. He'd have to take a seat for a moment. He told Scott he felt ill and made his way to a nearby bench to put his head in his hands. Soon he felt better and looked up briefly. Work had already begun on widening the road to put in a new bus lane. The noise was unbearable.

"Hey Matt! What ya doin'? Going all philosophical and goth on me here sitting like that?"

"I told you already."

"Dude, oh my God that was like four weeks ago. You've got to let her go. You said like last week you felt way better. Now we're back at square one?"

"Wait. No. Who? I told you I didn't feel well." He was lying. There was nothing wrong with him and no reason not to feel well. The bandage was gone and the road was oddly quiet again. Of course, there weren't any roadworks after all. Matt realized he hadn't shaved. Must have forgotten, though he'd been sure he had.

"Hey, Scott, I think something's screwed."

"What's screwed? Hey, you feeling alright? We can stop here at the ducks."

Matt didn't remember standing up. The gallery was a few dozen malicious metres behind them. The benches were on the other side. He felt gravel in his shoes. Damn it, he thought he'd got it all out. He felt a bit lightheaded. Okay. Wait a minute. Matt breathed and tried to make sense of it all. When he opened his eyes he saw a familiar face that wouldn't leave him in peace. The pressure on his chest was back.

"M, you okay? Dude it's only a watch. Take it off and don't worry. You'll repair it no problem. I know a guy who'll do it discount even." Matt glared at his friend and said nothing.

"Matt?"

He hadn't worn his watch. He looked down and was satisfied to see it wasn't there.

"What the hell, man? I'm not wearing jack shit. See. Stop asking if I'm okay, okay? I'm fine. I've been fine all day. You don't seem fuckin' fine."

He looked out over the distance of Hyde Park and back to the street. Scott wasn't there. A woman walking a German shepherd looked at him strangely. He'd have heard the guy move. No, of course, he was running alone. He couldn't remember why. Something here was desperately wrong. Was he having a stroke? Seizure. He pulled out his phone and turned it on. The screen glinted flawlessly. There was something he tried to grapple with just out of reach. Hallucinations. Family history of schizophrenia? No, not that he could remember. Drugs then? No drugs don't do this, not really, and not randomly on a run. Maybe he'd forgotten he'd taken them, or not taken his medication? After all this there was a cold sweat coming. Crap. This wasn't getting him anywhere. Matt took a breath and typed his password. At least that still worked. The background was a picture of him, Scott and the gang. For some reason he felt a twinge of sadness. That wasn't his picture. Nor was it in Scott's A to Z of online photographic masterpieces. He dialled.

"Which service do you require?" came a response.

"Ambulance." He heard himself being re-routed. Someone else picked up. He skipped their introduction.

"I think something's wrong. Hallucinations. Dizziness, like, this kind of schizophrenia."

Something strained somewhere in the eighth dimension. A shimmer refluxed down into the lowest four. A new offshoot of reality cracked into life, and the mixed ones shuddered, collapsed to death. The natural way to contain the weirdness and stop more harm was put into motion. The world fought back. Ripples of instability grasped and settled on the closest mind. At least the zero point was passed. The worst was over. A new Law of physics was made. It had to be made to stop the worst and was called up again like many aeons before.

In chess there are only so many games that can be played meaningfully. These are many, but not infinite. There are many possible realities and turns of events that run simultaneously, but not infinite, and not all worlds, universes, or collection of laws survive. The ones that do, adapt. Now a new game of chess was going to be played. Knights were suddenly allowed to move in an apocalyptically straight line. Only so many possibilities here too. There was only one way for a new reality to be created and for it to survive, a new rule. Some might wonder if it was still chess. Oblivious, Matt felt a shimmer and saw he was staring down into a manhole cover that was venting steam.

He bolted up as a reassuring jackhammer began to fire. Scott was next to him gasping. Half a cycle path stood nearby.

"What the fu-"

"Get away from me. You're not Matt."

"Rowenstein, it's me, mate."

"I'll beat your face in like the others, I swear to-"

"You had it too?" asked Matt.

"Yeah. You kept talking random sh-"

"So did you. Were you dead?"

"It made no sense."

"Same."

Scott Rowenstein stared at him. He grabbed Matt's arm and started pacing away from the bridge and towards Exhibition Road and the relative safety of home. Maybe relative is the wrong word. Matt checked his phone and put a hand up to his forehead as he was dragged.

Scott looked back. "Stop freaking out. Can you stop?" Matt's eyebrows rose in silent fear. No, it was still the same Scott.

"Nothing. Something you said. But didn't. You know."

"Weird visions? Yeah, I was out of it too. I thought I whacked you though. I think I did. I think maybe I hit you pretty hard. Mind the wildlife."

A mallard wandered by.

"And the ducks. Parasites they are," said Matt. The timing was just right. For the first time a certain Law kicked into place. At that moment forty miles away seven men in tweed were enjoying a fine morning on a majestic country estate. They crouched, knackered in the early summer air, aimed roughly and waited in the undergrowth for the other group to scare their prey into flight. Four fat birds took to the air. Seven huge bored double-barrelled shotguns scattered lead in unison. It was by all accounts terribly embarrassing. Everyone missed. And everyone would always miss from now on.

Had the ducks been omnipotent their quacks would have been fatally late. Deep beneath them Dr. Lana Peregrine got her latest set of results, left the accelerator to run. They were as expected. No real anomalies but some interesting potential new leads. She would need more time but nevertheless thanked her colleagues standing by the console for running the experiment for her in return for her doing their shift next week. They had a good idea what the next step in improving their experiment might be. None knew that now they'd never have a chance run it. All that was left for Lana was an oblivious mountain of paperwork. She reached for the radio.

"This is Echo Sixty. Everything looks good over here." She heard someone's voice on the other side who had a whole host of standard questions. "Yes, all readings are normal," she replied. "It seemed fine to me, but I'm no expert. We'll power down for maintenance in the evening. Thank you." The recalibration of the machine under the bridge would be done in the evening. But Lana still had some time before then.

***

Matt imagined what the unicorn would say, wondered if it would be pleased. He hears us now. He's lost his mind and now he can hear us, Lion. That's what it would say. And the lion might rumble, and it might turn around on its metal neck in its plinth and look him in the eye. Because for a moment on the bridge he'd seen the bus lane shining there with freshly-crimsoned tarmac and the one-way route signs. He'd been sitting when he remembered standing. There was one thought that was worse, and it was that one that he kept coming back to. You were dead, Scott, he thought. I was alone on that bridge because for a moment there, you were dead. Maybe you're alive now, but I was alone on that bridge and I remember why. He followed the dead man at a slow pace and passed out of the Unicorn's grounds to face Albert Hall. The dead man stopped.

"To the Union?" he asked Matt.

He nodded.

"We're going to figure this out, M. We're going to take the morning off today, and take some time. We've got time."

"I've got work later," said Matt.

"This is work."

"Real work." Matt looked beyond him. Dead man.

"Hey, I almost broke your jaw back there. That's what I saw. I floored you. I beat the utter living crap out of you. No, look at me. That happened," Scott pointed at him. "It wasn't an illusion, it wasn't some bullshit."

"I didn't see that."

"You didn't?"

"No."

"Do they serve breakfast at the Union?" asked Scott.

"Don't know."

They passed by Albert Hall, down the steps and beyond to the university buildings below. The whole thing was laid out neatly from up on those steps. You could see the rooftops of physics, the distant '70s computer science nightmare that soared over the skyline. They turned into a courtyard, and its old red-brick union buildings that housed the university bar. Bikes littered the entrance. You could smell the masked penny-pinching student life ingrained into the brickwork. Cut-price curry. Pizza. And booze. Disinfectant and a stiff courtyard breeze fought it and failed. Exquisitely mown grass tried its best to keep up pretences of a posh garden but hazard tape around broken branches of the trees told the truth. Scott passed through the courtyard and slammed open both doors to the bar. Glass shook, and Scott was glad when it held.

In the gloom there was a bartender, a handful of staff and the odd student group clustered in the corner. It was the sort of bar where the floorboard lacquer was gone and no-one remembered it ever being there. The TV's gave subtitled sports commentary in silence, and handful of staff set up tables. There was no breakfast today.

"I'm having a cider," said Scott.

"Will they serve you?"

"Do you want one?"

"If they serve you, sure."

Matt found a table and Scott returned with two cokes.

"No chance," said Scott. "They start at twelve."

Matt took his drink, finished half. "Explain to me what you saw," he said.

Scott shook his head. "I reckon maybe fumes from the vents or something," he said.

"Maybe. I felt awful, like my ribcage was about to give way,"

"I was going to have a good morning. Bit of a run. Put my pics online. Some films. Go out in the sun."

"No lectures then."

"Does it matter?"

"It does."

"No, I've got the day off." Scott seemed a bit better. Not dead then.

"At least it makes a story for the double A's," said Matt. The double A's were Amy and April, and both said no to runs. "Did you feel like you were about to get crushed?"

Scott nodded. "We'll let the girls know we've been tripping off hot vent steam all morning, and beating each other up. That's impressive that is, M. I approve." He paused to take a drink. Matt relaxed a little and pretended to plan out the rest of his day. He had a lab report, revision. Maybe he'd grab an Indian tonight?

"What were yours about?" asked Scott.

"It was full of you asking questions. That and like some weird health conditions."

"You were talking nonsense so I thought you were fake. It made sense at the time. I hit you hard. You hit back harder than I thought you could."

"How long did it last?"

"A few seconds, maybe longer. It kept, sort of, resetting. So I kept catching you by surprise."

"You didn't hit me, though."

"So who did I hit?" And that sentence hung there for a moment amongst the sound of tables and chairs scraping and the hoover preparing for the lunch rush. The answer was no one, or no-one that existed any more.

"Let's go have some breakfast," said Matt.