Jessica answers the phone without opening her eyes, knowing it'll be Sera—they've sworn to check in at least once a day, no matter what, until either Jess makes it to Sera's house or things go back to normal.

Or until the communications network goes down for good, of course, although they don't talk about that one.

'Hi,' Jessica says. 'I'm okay. You?'

'All good,' Sera says. 'Everything's still fine here. Where are you?'

'Grantham. I stopped at a hotel last night.'

'Are you sure? Have you checked?'

'Of course I—' Jessica starts, then realises what she's saying. These days, surety is rapidly becoming an obsolete notion.

She forces her eyes open and sits up. Instead of a narrow hotel bed, she's lying on a square bale of hay. A bag of sliced carrots rests on her lap and a small brown goat is asleep on her foot.

'Ah,' she says. 'Looks like it turned into a petting zoo in the night. Lots of goats.'

'I hate it when that happens,' Sera says. 'Sleeping through a displacement, I mean, not the goats. I quite like goats.'

She pauses. 'We could learn a lot from the animals, you know. They're not worrying and fretting and thinking up doomsday scenarios, are they? No. They're just getting on with it, because they know it's all going to be okay. They're more connected to nature than we are.'

Jessica holds out a carrot, which the goat nibbles at with tranquil contentment.

'I'm sure you're right,' she says, although she can't help thinking it probably has less to do with being privy to the secrets of the universe and more to do with lack of short-term memory. 'So this one didn't hit you, then, last night?'

Scientific study of the displacements is a new and mostly untested field. For at least the first few weeks, it was all written off as practical jokes, mistakes or overactive imaginations. It wasn't until Buckingham Palace became a theme park that it started to be taken seriously. But data is still patchy, and if there's a pattern to the way the displacements hit, nobody's identified it yet. One that turns a hotel into a petting zoo in Grantham might do little more than misplace a sock by the time it reaches Scotland.

'No,' Sera says. 'Well, not much. I mean, the house is a bungalow now, but that's okay. I don't think I left anything important upstairs. And it's grown a nice rear extension, so I've still got a guest room. And a Jacuzzi, now. So hurry up, eh? We can have a spa day when you get here.'

'That'll be great,' Jessica says. 'Okay, I'm getting back on the road now. If I don't see you tonight, I'll give you a ring tomorrow.'

She slides off the hay, wipes her palm free of goat spit and looks around for the exit.

Her own house had changed into a bungalow too, for a while. Then it disappeared completely. She came home from work last week and found a small, half-built shopping centre called the Myddleton Mall where her street used to be. It was kitted out with teeth-whitening booths, tanning salons and a fully-equipped Starbucks. At first she'd found that oddly comforting—could it really be the end of civilisation if you could still get a skinny, sugar-free hazelnut latte? But by the time she'd finished her coffee, the Starbucks had been replaced by a display stand advertising a will-writing service. Which hadn't seemed like such a good omen at all.

A little way along the path, there's a row of rabbit hutches. Standing behind them is a fifty-ish man in a blue suit. Pinned to his jacket is a name badge that says Derek.

'Good morning,' he says. 'Will you be checking out today?'

'Um. Yes?'

'That'll be thirty-four pounds, please.'

Jessica looks in her backpack. Inside is a cabbage, a pack of cards, and a Stephen King paperback.

Derek frowns. 'I'm afraid we only accept cash or cred—'

He breaks off, and when Jessica looks up again they're standing in what appears to be a tea room.

Jessica breathes out hard. New buildings can be bad, if they go up when you're standing in the wrong place—such as where the new fixtures and fittings are going to be.

In this case, the tea room's front door is a few inches to her left. A near miss.

She moves away from the door just as an old woman in a black raincoat walks through it.

'Hello there,' the woman says, pulling a scarf from her hair. 'Well, this isn't the chiropodist's, is it? Still, it looks like it might be more fun. I'm Betty, pleased to meet you. Shall we have some coffee and cake?'

Derek backs away and shakes his head. He goes on shaking it for a long time.

Betty shrugs and makes coffee for herself and Jessica using a state-of-the-art machine that looks like it performs heart bypass surgery as a sideline. Maybe it does. You never know, these days.

A couple of goats wander in. Jessica sets down a plate of muffins for them.

'Please don't encourage them,' Derek says. 'We don't have a licence to keep goats on the premises.'

'Oh, I don't think they're worried about anything like that, dear,' Betty says.

'Who?' Jessica says. 'The goats?'

'No, dear, no. The aliens. They're carrying out some kind of experiment on us. Or possibly making a reality show. They're probably up there right now, watching us.'

She waves at the ceiling. 'Hello there, I'm Betty. Vote for me. And thank you for the grandchildren. I always wanted some of those.'

Jessica glances up. So do the goats. Derek sits on the floor and puts his face in his hands.

Betty looks at him sadly. 'You're not going to win like that, are you, dear? Curling up in the corner and crying has been done to death, it's totally exhausted any entertainment value. They want to see people getting out there and making the most of it. Carpe whatsit, and all that. You need to start enjoying yourself.'

Derek stares at her. Then he curls up in the corner and cries harder.

'You just can't help some people, can you?' Betty says. She puts two mugs of coffee on a tray and takes it to one of the round tables. 'Come and put your feet up, Jessica dear. You look worn out.'

'Thank you,' Jess says. 'But I'd better be off. I've got to get to Edinburgh.'

'Edinburgh?' Betty gives her a doubtful look. 'Did you know Grantham station turned into a roller disco? Great fun, but not very practical from a travel perspective. Mind you, not many things are, lately. The A52 is nothing but molehills. At least, I think they're moles. Why don't you stay here? We could form an alliance. That usually wins some points.'

Jessica hesitates. The tea room is brightly lit and well-heated. It looks very cosy. Safe. And the overflowing trays of muffins do look good.

She glances at the door. Is there still a petting zoo outside? And if not, what's out there?

The last time she saw a television broadcast, a man in a suit stood outside the Houses of Parliament and said, 'Everything is under control. There is no cause for concern,' while Army trucks loaded up in the background. She hadn't been sure if she was watching a news report or a disaster film.

Maybe Betty's right about not travelling. Who knows, maybe she's even right about the aliens. It's as good a theory as any other Jessica's heard.

There was a website keeping track, for a while—Terrorists was the favourite, followed by Military Experiment Gone Wrong and Time Travel Accident. But the last time she was able to get online, the site was gone. Maybe someone went back in time and assassinated its creator.

She takes out her phone. It's a long while before the call goes through, but eventually Sera picks up.

'Hi. You okay? Everything's still good here.' Her voice is bright, but brittle. 'Well, apart from a little hitch at work this morning. Apparently we sell pet lingerie now.'

She gives a high, hitching laugh that goes on too long. 'Of course, none of us know the first thing about pet lingerie. We don't even know if it's legal, to be honest. So the shop's going to be shut while they look into it. That's good, though, because it'll give me a chance to get your room decorated. I reckon I'll have it all done by tomorrow.'

Her voice fades in and out. 'Jess? You'll be here then, won't you? Won't you?'

Jessica turns back to Betty, covers the phone with her hand and says goodbye. 'I'm on my way,' she tells Sera, and opens the tea room door. 'I'll be there soon.'

She doesn't bother checking out the station—she can hear Donna Summer blaring out from half a mile away—and while there are a lot of cars abandoned by the side of the road, the idea of driving makes her nervous. What if the car decides to be somewhere else while she's doing seventy miles an hour?

She decides she'd rather not find out, and starts walking.

After a few hours, when the light is starting to fade, she comes across a small, half-built shopping mall with teeth-whitening booths, tanning salons and a Starbucks. They've all been comprehensively looted, but it still triggers a pang of nostalgia. She decides to camp for the night, and goes to sleep behind the barista's station, with the one remaining bag of coffee beans as a pillow.

When the phone wakes her up the next morning, the ringtone has changed to a very loud and tinny version of 'Always Look on the Bright Side of Life'.

'Funny,' she says as she fumbles for it. Who knew the displacements had a sense of humour?

She swipes her finger across the screen and the music stops. 'Hi. I'm okay. You?'

'All good,' Sera says. 'Everything's still fine here, as usual. Where are you? You must be close, now.'

Jessica checks. The deserted Starbucks is still a deserted Starbucks. She picks her way across the broken glass littering the floor of the mall, and heads towards the exit. There's a sign above it that tells her she's in the Myddleton Mall, Islington.

She closes her eyes and lets her head drop. 'Funny,' she whispers.

'What? Did you say something? Jess?'

She lifts the phone back to her ear. 'Yes, sorry. I'm here.' She stares at the sign. 'I'm in Newcastle. Not far now.'

'Brilliant. Hey, did you see the telly was back on last night? They had the Prime Minister on the news, in that bunker thing. He said they've developed an algorithm that can predict the displacements. And MI5 are interrogating another bunch of terrorists, so they're bound to find out how to fix it soon. He said everything's going to be back to normal by Christmas. Isn't that great news?'

Jessica says, 'It certainly is. Okay, I'm getting back on the road now. If I don't see you tonight, I'll give you a ring tomorrow.'

What she doesn't say is that Christmas was last month.

Islington, if that's really where she is, has become a forest. The ground is springy underfoot, and covered with large, flat mushrooms. Jessica walks all day and most of the night, and eventually emerges into a clearing, which becomes a car park. She follows the exit signs to the back door of what appears to be a casino.

The door's unlocked, so she slips inside. All the lights are on, and the slot machines play a constant, jangly tune. One of them is flashing JACKPOT and dispensing streams of chocolates onto the floor.

Above the music, she can hear a sound that could be sirens. And another sound that could be gunfire. She looks around, but there are no windows.

She phones Sera. 'Hi.'

'Hi! Are you here? I've been looking out the window, but I can't see you.'

'No, I've got a little way to go yet.'

'Oh. Okay. Well, watch out—there's a big one coming. I can feel it in my chakras.'

Jessica tries one of the chocolates, but it tastes stale. She goes to the curved bar behind the slot machines instead. Her watch tells her that it's nine-thirty in the morning, but what does it know? What does anybody know?

She raises a glass under the vodka optic and holds it there for a long time.

'I lost the rear extension,' Sera says, 'but the back yard's turned into an orchard, so that makes up for it. When you get here, we should learn how to make cider.'

'That'll be fun,' Jessica says. The popping sound, which might or might not be gunfire, gets louder.

'Although of course, it might all be different by then,' Sera goes on. 'It could be under water, and we'll have to learn how to surf. Or it'll be a Grand Prix circuit, and we'll be driving race cars. Or a Siberian tundra, and we'll be herding yaks.'

Jessica swallows half her drink and winces at the burn. 'Do they have yaks in Siberia? I thought that was Mongolia.'

'Good point, I'm not sure.'

The wailing sirens make one last tortured shriek, then go silent.

'It doesn't matter,' Jessica says. 'Because you're right. We'll learn how to make cider, or surf, or whatever else it is we need to do. And if we get yaks, Siberian or otherwise, we'll herd them.'

The slot machines start toppling over like dominoes. Somewhere, it sounds like large sheets of glass are breaking.

'What's that noise?' Sera says. 'Jess? What's going on?'

'It's nothing,' Jessica says. 'Probably the telly.'

Outside, something explodes. The casino lights go out and there's a strong, pungent smell of smoke.

'Are you still there?' Sera says. She sounds impossibly far away. 'I can't hear you.'

'I'm here,' Jessica says, but she can barely hear her own voice over the static on the line and a low, groaning sound from outside that she can't identify.

'What noise do yaks make?' she asks, but if there's a reply, she can't make it out. 'Sera? Are you there? Sera?'

She shakes the phone, but the connection's gone dead. There's no sound at all now, not even white noise. She downs the rest of her vodka and the empty glass slips from her hand. It shatters on the floor.

Jessica steps over it. 'Okay, I'm getting back on the road right now,' she tells the dead phone, in her firmest voice. 'And if I don't see you tonight, I'll give you a ring tomorrow.'