I arrived back in 2017 wet-cheeked and in an emotional shock so profound I barely recognized it for what it was. And then I lay on the ground beside the tree for who knows how long, panting like a cornered animal as my mind tried to reconcile what just happened to me.

And what had just happened? If I wasn't insane, or under the influence of some new designer psychedelic, it seemed that my best friend Paige Renner had taken me briefly back to the 9th century, so I could see that she, her baby and her father were happy, and that they had chosen to stay in the past. She did it so I could have some peace of mind, so I wouldn't spend the rest of my life assuming some terrible fate had befallen them.

I'd been robotic during our goodbyes – and during the short time I'd spent in the place whose existence I had flatly and resolutely disbelieved in when Paige first told me about it. And now I was flat on my back in the middle of the woods in 2017, out of breath although I hadn't been running and conscious of my brain looping helplessly round and round an irreconcilable pair of facts: first, my intellectual knowledge that time travel wasn't possible and, second, the reports of my five senses over the course of the afternoon. These reports were unambiguous – not only was time travel possible, I'd experienced it. It had just happened to me.

At first there had been nothingness – only the dark, airless whoosh that enveloped my entire body when I lay my bare hands on the tree. It would have had me clawing at my throat in a panic had it lasted even 1 second longer than it did. And after that there was another wood – not the one I had been in a moment before. This new wood was thicker, darker, and there was no ambient traffic noise in the background. There was, however, something familiar about it. It was the smell – the acrid wood-smoke, the faint marine tang of the ocean. My body knew I was in England, thousands of miles away from New York State – where I been only moments before – before my mind was prepared to accept it. England. Home.

But the people Paige introduced me to were not like any Englishmen I had ever met. Their accents were thick and almost impenetrable, they were short and dirty and strangely careworn in a way I was used to seeing only in the very, very old and even then only in those who had lived hard lives.

Paige can't have arranged all that, I thought to myself as the stars winked into life over my head in the present time. There's no drug that could do that, no magic trick. It must have been real – even though it can't have been real.

Eventually, getting cold, I staggered to my feet and made my way slowly and quietly back up to the Renner's house – a house that looked even darker and emptier now that I knew its occupants were never coming back – and to my car, which I had parked a little ways down the road so as to avoid the attentions of the reporters who were still camped out on the property next door, hoping to get a shot of Paige with her baby son.

But just as I turned the engine on the interior of my little Volkswagen Golf was suddenly brightly lit and a second later the sounds of running footsteps and shouted questions filled my ears.

"Have you seen Paige Renner?"

"Have you seen her baby?"

"Can we ask you a couple of questions?"

When one of them recognized me and began to pound on the driver's side window, yelling my name, I slammed the car into gear and gunned it away from there as fast as I could, shaking with what I wasn't sure was the chilly evening or the experience I'd just been through or the sheer, predatory intensity of the reporters. The media knew who I was, they'd followed me home a few times on campus and hassled a few of Paige's other friends. I was even aware that I played quite a prominent role in some of the crazier conspiracy theories online – my favorite of which must have been the one that claimed I was an inter-dimensional being, sent to earth to befriend human women and facilitate their impregnation by an alien race.

I smiled as I zoomed down the dark country lanes outside River Forks and tried to picture the looks on the faces of all those internet crazies if they knew the actual truth.

If I'd known what was coming – and maybe I should have – I can tell you, I wouldn't have been smiling. The next few days probably looked uneventful from the outside. It was the beginning of my senior year at university in America, and the routine of going to classes, seeing friends, studying, was starting to settle into me again after the summer. What happened to me that afternoon with Paige Renner and her dad put a stop to any of that collegiate normality. I went to my classes out of habit, walking unseeingly across the gorgeous old campus as the first yellowed leaves of autumn floated down around me, trying to think of anything but the impossible thing that had happened to me and failing completely. People noticed. Friends noticed. When they asked me what was wrong I lied and told them it was nothing, I was just nervous about my future, wondering whether I should apply to graduate schools in America or back in the UK.

Is this how Paige felt? I asked myself, wracked with guilt at how I'd reacted to her confession that she'd spent most of her life time-traveling back to 9th century England. Did she feel this alone? Like she was going to burst with the secret she knew she couldn't tell anyone? Well – until she told me and I treated her like a crazy person.

A few days after the trip, as I had begun to refer to it in my own mind – because calling it a 'trip' made it sound almost mundane, like a trip to the shops, or the beach, or, you know, the 9th freaking century – my parents called on a Wednesday night. They usually called me on Sunday nights. When I asked my mother what was wrong, she didn't reply right away. When she did, she told me she had been about to ask me the same thing.

"What?" I asked her, confused. "Why would something be wrong with me? Why are you –"

"Well, your friend Jenny called us," my mother started. "She called us last night and –"

"Wait. Jenny called you? When? Why?"

Jenny was one of my closest friends at Grand Northeastern – probably my closest friend now Paige was gone – and the only other English person I knew in America. She was from Liverpool and she had an earthy northern-ness about her that I had liked right off the bat. But what the hell was she doing calling my parents?

"Oh she was sure it was nothing to be worried about," my mother replied breezily, the way she does when things are anything but breezy. "She just thought that, uh, she thought maybe there was something upsetting you. That you seemed a little quieter than usual."

My mum was full of it. I knew it, and she must have known I knew it. My parents are the opposite of the classic American 'helicopter' stereotype – their whole deal from the time I was very small was to avoid coddling me, to allow me to learn independence, to refrain from protecting me when it came time to learn hard lessons. My parents didn't call out of the blue because someone told them I seemed 'quieter' than usual.

"I don't even know what that means," I answered, annoyed at Jenny for meddling. And then, when I tried to continue my sentence, to crack some joke about Jenny being a little dramatic, something awful happened. My words stuck in my throat suddenly and I realized with some small degree of horror that I was on the verge of crying.

"What is it?" My mother asked, hearing the way my voice had trailed off into a weird strangled noise before I could finish speaking. "Emma?"

I swallowed once, and then again. I blinked my eyes. I breathed in, slowly, and then out again. Nothing helped. The lump in my throat got bigger. What the hell was I doing? Crying? What the bloody hell was I crying about? I think I was even more astonished than my mother was.

"Sorry," I whispered. "I'm sorry Mum, I'm –"

"Emma!" My mother exclaimed, having it confirmed by my pathetic whispering that I was in fact weeping. "Darling, you must tell us what's going on right now! It's been years since I heard you crying, Em. Come on, out with it. What's gotten my lovely girl so emotional?"

I didn't quite know the answer to that question. Was it the trip with Paige? It must have been. But why was it manifesting itself in these sudden, embarrassing tears? I didn't know that, either. What I was definitely did know was that I couldn't tell my parents the truth – not unless I wanted them to react the way I had when Paige told me. Not unless I wanted them to think I was losing my marbles. No. So I had to tell them something else.

In the end I came up with some ridiculous and barely believable story about being worried about my grades and whether or not I was going to get into the graduate school of my choice. Not that I had ever worried about my grades before in my entire life. It was just what popped into my head that evening, as I tried desperately to reassure my mother that I wasn't about to have some sort of emotional breakdown.

She didn't believe me. Neither did my dad. I could hear it in their voices. But as I couldn't tell them the truth and as I think they sensed they weren't going to get any further information out of me that night, we ended the call a short while later and I retreated to my tiny little student bedroom to worry about whether or not I was going to have that breakdown.

Less than two minutes later, my phone rang again and my heart skipped a beat when I saw the name on the screen:

River Forks Police Department

My thumb shook wildly as I took the call, instantly regretting not letting it go to voicemail when my voice proved just as shaky as the rest of me.

"H – Hello?"

"Is this Emma Wallis?"

I swallowed hard, and my throat made an audible clicking sound. "Yes."

"Ms. Wallis, this is Sergeant Halson with the River Forks Police Department, we're just wondering if we can ask you a few questions about your friend Paige Renner?"

Damnit. I could have kicked myself. Of course the police – of course everyone – was eventually going to notice that Paige was missing again. And that this time she was missing along with her newborn son and her father. If I hadn't been so busy obsessing about what had happened to me, I would have been more conscious of this.

"Um" I stammered, worried that I sounded guilty even as I knew I hadn't done anything wrong. "Um – yes. Yes, sure. That's fine."

Sergeant Halson paused, which I interpreted as him noticing how nervous I sounded – and that just made me even more nervous. "OK Ms. Wallis. It's just that no one has heard from Paige – or her father – for a few days now. We're going to send someone around to the house for a welfare check but I'm just calling a few of her friends first, to see if they have any information."

My body was hot and cold at the same time. Was I going to have to lie to this man – a police officer? I was. Why hadn't I thought of this earlier? Why hadn't I prepared for this?

"OK."

"Can you tell me when the last time you saw Ms. Renner was?"

"It was a few days ago. At her house. At, uh – at her dad's house."

"And can you give me an exact date if you can, Ms. Wallis?"

Sergeant Halson wasn't being overbearing or unkind, but there was a seriousness in his voice that unsettled me. I could have given him an exact date, but I chose to keep things vague, to give myself some time to come up with a workable story.

"I'm not sure – um, it was recently, though. She was with her son and her dad. It was at their house."

"Yes you already said that."

"Oh, did I?"

"Yes."

A light sweat broke out on my forehead but I wrestled myself into what could pass for composure and didn't say anything further. A short, awkward silence ensued before the officer spoke again:

"Alright Ms. Wallis – thank you for your help. I trust you won't mind if we get in touch again, if we have any difficulty reaching your friend?"

"No," I replied as a knot of dread formed in my stomach. "No, that would be fine."

When the call was over I lay back on my bed, fruitlessly trying to get the jumbled mess of thoughts in my mind into some kind of order. That cop was going to call back, that much was certain. Because Paige wasn't going to show up, and neither was her father or her son. Sooner or later – and probably sooner, given the interest in the whole saga of Paige Renner and her mysterious, previously temporary disappearance – everyone was going to realize that she was gone again. And then they were going to lose their minds. Police, media, the public – everyone.

For the first time since Paige had brought me to the tree in the woods at the bottom of her yard and from there taken me to the 9th century, I felt a flash of anger towards her, although it was immediately replaced with guilt. What right did I have to be angry with her if the possible consequences of my involvement in her second (and completely voluntary) disappearance hadn't even fully occurred to me until Sergeant Halson called?

I went to bed that night in a terrible state, so stressed out I could barely sleep before dawn broke, and then spent the next couple of days like that. Eventually I got so tired I had to sit down one afternoon in the living room of my rented flat and seriously consider what I was going to do.

The first thing I forced myself to accept was that I hadn't done anything wrong or illegal. I hadn't. So the next time I spoke to the police – and I knew there would be a next time – I had to keep that thought in mind, so I didn't come across like a nervous wreck again and give them a reason to suspect me. The second thing I did was make a pact with myself to set aside the knowledge I now had, from my excursion into the deep past. I couldn't live with it sitting out there in the open space of my psyche, it would drive me mad. And I couldn't deny it, no matter how hard I tried to come up with alternate explanations for what had happened that afternoon in September. So what I did was tuck it under the mental rug, out of sight, to be dealt with at some later time. Some time when I didn't have papers due, parties to attend and graduate schools to apply to.

Looking back, I see what a futile gesture it was. But I'm English, for better and for worse. For better, I have a charmingly dry sense of humor and people find me kind and warm. For worse, I can rely much too heavily on the 'sweep it under the carpet' school of emotional wellbeing. And that doesn't work for the kind of secret I had then – huge and terrifyingly real.

For awhile, through midterms and into the second half of the fall semester, it seemed to work. Sure, I was a little more irritable with my friends, a little quicker to frown or snap than I had been before. And I started to experience terrible headaches that would come on in the late afternoons and spread their tentacles of pain up the back of my neck and around my skull until my whole head seemed to be one big, throbbing locus of agony. But there was ibuprofen for the headaches and excuses for my friends.

* * *

Within a couple of weeks of Paige's second disappearance, the police knew. And shortly after that, the media knew. And once the media found out, everything went crazy. Grand Northeastern hired security guards to escort myself – and a couple of Paige's other friends who had made the mistake of speaking to the media (and thereby making themselves recognizable to the general public) the first time she vanished – to and from our classes. Our social circle closed tightly around us, too, a protective barrier of an emotional and often a physical kind. I watched more than once as the people who cared about me chased prying reporters away from bars where they had tracked me down. Once, one of my professors almost came to blows with a man from one of those sleazy gossip websites as he surreptitiously tried to snap photos of me through the window in the classroom door. My parents hired a lawyer to act as my representative when dealing with the police department and, eventually, the FBI.

Nobody let me down. I was as lucky as it's possible to be in the middle of an epic shit-storm like that. But it wasn't enough. The stories were impossible to avoid (even as I tried to do so) the headlines blaring out from countless different websites, blogs, newspapers, TV news shows, evening talk shows, conversations outside classrooms that would go awkwardly silent as soon as the participants spotted me.

I lied to my parents, my friends and myself. I told them it was fine, that I was fine.

But I wasn't fine. And it began to manifest itself in strange ways. For one, I became obsessed with the time period of the Viking invasions of England. Not obsessed in the sense of reading a book here or there or watching a documentary every couple of weeks. No, I became obsessed to the point of skipping classes to Google various locations, known battles, key figures from that time in British history. I started heading straight to my room as soon as I got home every evening, and skipping college parties with my friends, in order to read further into my new area of interest.

I also started driving to River Forks on a regular basis, down the road the Renner's house was located on and slowing to a crawl as I drove by, irrationally hoping to see a light on inside, or maybe Mr. Renner out in the driveway, spreading salt on the thick layer of ice that formed on every surface during that cold winter.

One time, I even parked my car on the road that bordered the Renner's large property on the other side, away from the eyes of the police that were still to be found lurking outside a few days a week, either sitting quietly in their cars or looking around the yard. It took me half an hour to walk through the snowy, overgrown field to the woods, and then I almost got lost, disoriented from only having been on that part of the property once before. But eventually, I found the tree and then I stood there for a long time – until I could no longer feel the tips of my fingers or my toes frozen in my boots – with a feeling of desperation in my heart.

I missed Paige. I would have missed her anyway, even if I hadn't known exactly where – and when – she was. But her absence was even more acute for knowing she was the only person on earth I could possibly talk to about what I was going through. And she was gone. As thoroughly gone as she would have been had she died, or been kidnapped again by the aliens who then took her and her father and her half-human, half-alien baby back to their home planet (which is exactly what happened, according to certain websites).

The tree was right in front of me. In my feet was that strange, aching pain I sometimes get when standing on high cliffs or ledges, that feeling of being half-convinced your own brain is going to go rogue and convince you to throw yourself off the edge before you even have time to think about it. In my hands was an itch, an urge to reach out and touch one of the tree's roots or even its rough, thick trunk. But I didn't. I couldn't. No more than I could jump off a cliff. For one thing, I couldn't stay there the way Paige had. How would I explain my absence when I got back? I'd seen what Paige herself had gone through. And what about the 9th century itself? It would be insane to go back there, where marauding Vikings and possibly-hostile locals lurked, unbound by modern laws against the kidnapping of strange women.

Still. I wasn't there in the woods because I wanted to escape my modern life. Everything that was happening at the time was a trial, but I wasn't in the same boat Paige had been in as a child, with one parent dead and one unable to care for me, no friends, no social life. I was there because I couldn't believe what had happened. You'd think you would. You'd think literal, physical proof would be enough. And then you go back in time, return to the 21st century, and over the next few weeks the sheer power of knowledge – of knowing that something like that isn't possible – begins to go to work on your battered mind, replacing what your five senses told you was true. I could feel it happening to me, the way I'd already begun to half laugh at myself, internally, when I thought about the way Paige's friend Eadgar had looked. I would picture his dirty, bare feet and his nearly entirely toothless grin and smile a little sheepishly. That can't have happened, a voice would whisper. Your mind is playing tricks on you. You imagined it. Or, if you didn't imagine it, your memory is exaggerating things. You know this, you've read about this – how unreliable memory is. Why would you be an exception?

It was easier to believe the voice. I knew if I kept believing it I might one day be able to tell myself that the whole episode was some kind of hallucination. But even as I began to go along with the cajoling doubts, I couldn't forget what had happened. I couldn't forget that feeling of losing my breath, tumbling through a darkness thicker and more fathomless than any earthly midnight. And then the smell of those woods, of the sea – the smell of home. How could it be that in one moment I was standing on American soil, and the next I was home – in England? It couldn't be.

I took a small, unconscious step towards the tree. Maybe I could just make sure? Maybe if I put the tip of one finger on it I might feel that blackness trying to suck me in again, and pull my hand back before it took me?

Maybe, maybe, maybe. No. I stepped back, turned away, and began the long trudge back over the field to the car. There was a heaviness in my heart matched only by the heaviness of my body – it seemed to take more effort than usual to lift one foot in front of the other. It was the weight of a secret – the kind of secret that needs to be shared at the same time it can't be, because no one would believe it.