Obelisk

by Stephen Baxter

  ‘If they’re changing the past,’ Penny said, ‘why would we remember? Our memories should be changed too.’

  ‘Good question,’ Amanda said respectfully. ‘Maybe any changes to the time stream are localised – the effects travelling no wider than the rats need them to be. After all, time travel must be energy-consuming. In general it ought to be a last resort. Maybe the time-travel reflex cuts in only as an emergency option when the rat is cornered. We might be able to use that to test them …’

  But Penny absolutely vetoed doing any kind of experiment that would put her rats under stress.

  I couldn’t really have cared less about rats, even time-travelling rats. But it was a pleasure to come home after another dull day with dusty solicitors to help Penny with the rats’ feed or with cleaning them out, and to talk over their latest exploits. ‘Who would have thought,’ said Penny, who could be disturbingly wise beyond her years, ‘that a pair of glow-in-the-dark rodents would bring us together?’

  And then there was Amanda. At first it was odd to have a woman of my own age around the house again. Even after weeks with us she was awkward, oddly shy, but with that sharp brain and a healthy dose of empathy she was always good company.

  I did try to find out more about her. ‘You said you did a PhD. Wouldn’t you rather be working in a place like RAL, than with rats and schoolkids?’

  ‘Not me.’ She pushed back her hair. ‘Academia is a pretty brutal world, you know. Petty bullying when you’re junior, and lifelong rivalries when you’re older.’

  ‘Like a rat pack,’ Penny said.

  ‘Oh, academics make rats look civilised.’

  She seemed to enjoy our company in turn, as long as we had the rats as neutral ground between us. She evidently had nobody at home, no partner or kids. Penny clearly hoped that some kind of relationship was going to bloom between us, that her mother would be replaced in her life’s hierarchy of security by a favourite teacher. It wasn’t impossible. I was drawn into those seawater eyes. But I could see nothing but complications, and held back, taking it slowly.

  Too slowly, in the event. In the brief time we had left, I learned little more about Amanda’s past and her private life, and nothing about her few sad, failed love affairs. For in the end, of course, the rats got in the way.

  On the day Appleton gave birth, Amanda stayed with us late into the evening, as the rat suckled her babies, a dozen of them.

  It had been about seven weeks since we’d brought the rats home from RAL. It was early June now, and the evening was long, the air through the open window fresh and full of the scent of cut grass. Didcot’s not an exciting place, but on a warm summer evening, with the birds singing and the lawns green, middle England is as pretty a place as you’ll find anywhere. And the baby rats had made Penny happy. It was a good day, and by about eleven p.m., hours after the rat had given birth, I felt pretty mellow, and was vaguely wondering how I could arrange for some time alone with Amanda.

  Then Penny broke the mood with a sudden scream. Amanda and I rushed to see what was wrong. Of the dozen babies, only two remained in the cage with Appleton, who seemed to be sleeping soundly.

  Penny was distressed. She thought the babies must have been eaten by their mother, a gruesome thought, and I hugged her.

  But Amanda calmly pointed out there was no evidence of such cannibalism. ‘If Appleton had eaten all those babies,’ she said reasonably, ‘we’d have heard, and we’d see the by-products. The mess.’

  ‘Then where are the little beggars?’ I snapped. ‘We’ve been sitting by this damn cage all day. Baby rats don’t just disappear—’

  ‘Baby rats just appeared,’ Penny pointed out. ‘Inside the accelerator, remember? Maybe they time-travelled out.’

  Now, given what had gone before, that was a reasonable suggestion. But with my mood shattered I’d had enough of mutant rats. I snorted, and as Amanda and Penny exchanged glances, I turned up the lights and started a more conventional search around the room. I soon found a hole, gnawed through the skirting board. When I dug into the hole with a probing finger, I found bits of paper, stinking of urine. A rat nest.

  I sat back on my heels, looking at the hole, and Penny and Amanda joined me.

  ‘Baby rats can’t gnaw holes that size,’ Penny said.

  ‘Adults can,’ said Amanda. She ran a finger around the rim of the hole. ‘The nest looks weeks old to me. Three or four?’

  ‘The thing is,’ I said reluctantly, ‘I checked this board this morning. I checked the whole room. I usually do. There was no hole here. I’m sure of it. And certainly not a three-week-old nest.’

  Penny grasped the situation immediately. ‘The babies travelled back in time, three or four weeks. They went back in time, and built a nest here and grew up.’

  Amanda nodded. ‘They changed the past. So a nest exists here now where it didn’t before.’

  ‘Oh, come on,’ I said. ‘What happened to Occam’s razor? Isn’t it simpler to suppose that we’ve just got another bunch of rats, that just happened to show up now – or were drawn by the scent of Rutherford and Appleton?’

  Penny shook her head. ‘Won’t wash, Dad. That doesn’t explain the way the hole just magically appeared.’

  Amanda, kneeling down, was still inspecting the hole. ‘I wish I had a torch … I can’t see evidence of more than a couple of animals here. Three at the most? But we lost maybe ten of our dozen babies. So where are the rest?’

  Penny ran to her tablet and immediately began scanning news sites, blogs, police and health resources, for unusual sightings of rats. That night there were four sightings in the Didcot area – four encounters with rats where no rats had been seen before, big, aggressive animals that were hard to catch. One report claimed a rat had attacked an infant in her cot. Penny looked at us, her eyes shining in the screen’s silver light. ‘Oops,’ she said.

  Amanda stood up. ‘I think it’s time we took this a bit more seriously. Penny, do you mind if I take one of these babies into RAL for some tests? I have contacts there …’

  That was week seven, as we started to count it later: the seventh week since Penny first spotted those baby rats in their sealed-up sphere at RAL.

  The sightings of the rats continued through spring and summer, spreading out through Oxfordshire and Berkshire, the range increasing by roughly a couple of kilometres every three weeks. Penny and I set up an Ordnance Survey map on the wall of the dining room, and tracked the sightings with sticky coloured dots. By the beginning of September – week twenty – our dots had got as far as Abingdon, about eight kilometres away. The attacks on food stores, pets, livestock and, unfortunately, people, were getting more serious, and there were reports of the creatures causing other problems by gnawing through power lines, telephone optic-fibre cables and plastic water pipes. The rats were ferociously difficult to kill or contain, baffling the vermin controllers. The health authorities and the police were considering quarantining off an infected zone to try to stop the spread of the tabloids’ ‘super-rats’.

  Amanda came to visit us on the first Saturday in September, the last weekend before school started again – although it wasn’t yet clear if the schools would open because of the continuing rat problem – and brought back the baby she had borrowed for testing in a cat box; it was now fully grown. Rutherford, Appleton and their unnamed babies, now separated by sex, watched impassively.

  Amanda professed admiration for our map.

  ‘Look,’ Penny said. ‘We used a different colour code for each week since I found the first two at RAL. See how it spreads out? And there’s more of them all the time. I counted it up with Dad. There were four nests sighted that first night when the babies were born. Three weeks later there were twenty-six. Three weeks after that a hundred and twenty-eight …’

  ‘Show her your graph,’ I said.

  Penny brought up a graph of the number of reports of ind
ependent nests versus time, plotted on logarithmic scales. There was a scatter of points around a neat straight-line trend. ‘Dad showed me how to do this. See that? It’s a power-law line. That’s what Dad says. Every three weeks the nests seem to multiply by about five. So it grows quickly. This is week twenty and we’re up to over three thousand, spread across a circle about sixteen kilometres wide.’

  Amanda nodded. ‘You should show this to Mr Beauregard. He keeps saying you’re underachieving at maths.’

  She pulled a face. ‘This isn’t maths. This is real.’

  Amanda raised her eyebrows at me. ‘Which tells you all you need to know about Bob Beauregard’s teaching methods. That fivefold increase maybe makes sense. You get typically ten or a dozen babies per litter. Maybe five breeding pairs each generation? But the generations are coming too close together, though, even for these rats … I’ll have to think about that. Do some mathematical modelling.’

  I went to put the kettle on. ‘So how’s the youngster? Survived its tests at RAL?’

  ‘Oh, yes.’ She leaned down to look at the rat in its cat box. ‘Although my friends in there couldn’t agree on an interpretation of their scan results.’

  Penny said, ‘Tell us what you think.’

  Amanda said slowly, ‘Well, I think this rat has got a wormhole in its stomach. A flaw in spacetime. And I think it was born that way, born with the wormhole.’ She smiled at us. ‘Isn’t that a wonderful idea?’

  Penny clapped her hands.

  I poured out mugs of tea for me and Amanda, handed Penny a soda, and we sat at the table. ‘“A flaw in spacetime.” I’m not sure what that means.’

  ‘The classical description of a wormhole is the Einstein-Rosen bridge, which—’

  ‘Einstein didn’t keep rats, as far as I know. This, this flaw in its stomach, is how the rat can travel back in time. Is that what you mean?’

  She nodded. ‘But not voluntarily, I don’t think. It must be connected to the rat’s nervous system somehow – like a muscular reflex. When it’s cornered, it flexes this spacetime spring, and flips back.’

  ‘Just a few seconds,’ Penny said.

  ‘Yes. That would be enough to escape most entrapment situations. But I’m speculating that a deeper reflex can work when the rats are very young. What if some babies in a litter can hop back weeks? It would be a random jump into the unknown, but at least they would be safe from any predators who might be attracted to the nest.’

  ‘Or the vermin controllers.’

  ‘Well, yes. And we know this strain of rat is able to survive precociously young – especially if it finds some kind human like Penny to look after it.’

  Penny frowned. ‘They’d be separated from their mother. For ever.’

  ‘But rats don’t have the same kind of parental bond as we do, Penny. We, with our ape lineage, only have a few children, whom we cherish. The rats have lots of babies, expecting to lose most of them to predators. Being able to throw at least some of your babies back to the safety of the past is a valid survival option.’

  I said, ‘And this is what the RAL people wouldn’t believe.’

  ‘Well, would you? Although you’d think by now others would have noticed something odd. The police and the rest keep saying they’re just an extreme strain of ordinary rat.’

  ‘So how did spacetime wormholes get into the bellies of rats?’

  ‘It started – or will start – in the place we found the first pair.’

  ‘The Pevatron?’

  ‘You recall those anti-science protesters outside the facility? They may have a point. The Pevatron will work at unprecedented high energies, and even some of the RAL people are expecting it to create extremely exotic objects …’

  Objects such as wormholes and black holes, she told us. The energies released by the Pevatron’s colliding electrons and positrons could be enough to rip the fabric of spacetime and leave it stitched back together again wrong, with points that should be separated in space or in time unnaturally connected together.

  ‘Miniature time machines,’ Penny said.

  ‘Yes. The RAL people are actually figuring out ways to detect such things. If a particle got trapped in such a wormhole it might bounce back and forth so you’d see multiple copies of it. Or, you might see a flash as all the light that fell in the wormhole in the future, as long as it existed, was sent back to the instant of its creation and emerged all at once.’

  I nodded, half understanding, not quite believing. ‘And if such a wormhole did form, at high energy …’

  Amanda spread her hands on the table. ‘I’m speculating. You’d get not one but a whole population of the things. The wormholes would interact and self-select – I think we might see a kind of evolution, a physical evolution, as the wormholes spiralled into stable, low-energy modes that could persist even outside the Pevatron, in our low-energy environment.’

  ‘Until one got swallowed by a rat,’ I said sceptically.

  ‘Well, something like that. After that we’re talking about biological evolution. It’s obvious what a competitive advantage an ability to time-travel would confer. And, remember, if these creatures are somehow looping back in time, a lot of generations could be compressed into a short interval. Evolution could work very quickly, the time-travel gene spreading fast.’

  ‘OK. But even if I buy all that, the Pevatron doesn’t work yet. It isn’t due to come online for two whole years! So how did those first time-travelling rats end up back in April?’

  ‘That’s obvious, Dad,’ Penny said, admonishing. ‘They come from the future. They are infesting the past.’ She smiled at the idea. ‘Cool.’

  Amanda and I shared a glance.

  That didn’t seem so cool to me. Mankind has waged war against rats since we became farmers. Even before the Pevatron rats came along, there were thought to be more rats than all the other mammals put together; and rats and the diseases they brought were thought to have killed more humans in the second millennium than all our wars. If this new strain really did have the ability to time-travel – even to plant their young in the deep past – how could humanity stop them?

  We weren’t about to alarm Penny, who clearly hadn’t thought it through that far. I raised the pot. ‘More tea?’

  A population increasing fivefold expands fast. By the end of September there were over fifteen thousand nests, being spied as far out as Wantage. That was when we were evacuated out of the expanding infestation zone. It broke Penny’s heart when Rutherford and Appleton were taken away.

  Amanda sent us a video clip. It had been caught by chance, by a webcam in a bird’s nesting box: it was the arrival of a baby rat, apparently sent from the future into its past, our present. At first you saw a sort of outline, flattened like roadkill, that gradually filled up to become a living, breathing, three-dimensional rat. Amanda said it was as if the rats were using their wormhole muscles to fold up into a higher spacetime dimension, and then back down into ours. She had hacked this footage out of data being gathered by government science units at the heart of the infected zone. The scientists didn’t know what to make of it – or if they did, they weren’t admitting it.

  By week twenty-nine, mid-November, the rats were being seen in Wallingford, around thirteen kilometres from Harwell. In our government-issue caravan we kept up our map, and the centre of it was covered with dots; the rats weren’t just spreading outward but were filling in the spaces they had already colonised. The authorities estimated there were over three hundred and fifty thousand nests in the area. Penny extrapolated her graph and made lurid predictions of how quickly the rats would reach Birmingham, London, the Channel Tunnel. ‘It’s the end of the world, Dad, for humans anyhow,’ she said, thrilling herself by half-believing it.

  By the end of November, the authorities were making provisional plans to evacuate Oxford.

  That was when Amanda called me and a
sked me for help. ‘We need to sort this out before it’s too late.’

  I met her at the edge of the control zone, near Wallingford. She had requisitioned an NHS ambulance, rat-hardened with cages over its tyres and netting over its doors. She was already wearing her spacesuit, as she called it, a coverall of tough Kevlar fabric with thick gloves and a hood like a nuclear engineer’s. She had one for me; I had to put it on as she drove us briskly into the zone. I was impressed by the resources she’d assembled, through leaning on her contacts within Harwell itself. She was always far smarter, more resourceful than she appeared, and was rising to this challenge. She was having a good war. That’s one reason why I’ll miss her.

  Inside the infected zone the towns and villages were deserted of people. The rats were everywhere, swarming out of doorways and windows and over the streets in a black tide. Even out in the country I could hear their heavy bodies thumping against the chassis of the ambulance as we drove.

  ‘They’ve eaten everything there is to eat,’ Amanda said. ‘The supermarkets, larders, granaries, fields, all stripped. The population must be near its peak. Soon they’ll turn on each other, if they haven’t already …’

  As we neared Harwell we passed the hub of the emergency control, a heavily fenced-off group of trailers, vehicles and comms masts – Gold Command, as it was called, under the control of the local chief constable, and patrolled by squaddies armed with rifles and flame-throwers. Rats scurried across the ground even inside the soldiers’ perimeter. That was the nature of them.

  At Harwell itself we left the ambulance at RAL’s security gate, were passed through the unmanned security barriers by Amanda’s retinal scans, and walked across a campus deserted save for the shadowy black forms of rats. Amanda wore a canvas pack on her back that looked suspicious even to me, but none of the campus’s security measures impeded us.