“The train is now approaching the station, please gather together your personal belongings and check your tickets once more …”

I rubbed my eyes and stretched. Were we nearly at the station already?

Outside the train window, the dark wings of night had already settled over the earth. A fine layer of mist seemed to coat the glass. Looking out, all I could see was the hazy impression of my face, and occasional flashes of lamplight.

“Excuse me, sir, please show me your ticket.” I hadn’t noticed the train attendant appearing at my side. She was wearing a knitted vest and she stared at me unblinkingly, eyes wide open.

“Hm? We’re nearly there but you’re still doing ticket checks …?” I muttered as I thrust my hand into my trouser pockets, then opened my khaki-coloured briefcase. Where had I put it?

“Ah, here it is.” I produced the pink slip of paper from amongst my project proposal documents, which had been thrown into disarray by my rummaging. “Xi’an North Railway Station to Beijing West Railway Station, right?”

“No, not that ticket. I need to see your special express ticket.”

“Oh? Isn’t this the G674 service?” I checked the ticket, which clearly read: Train service G674, Xi’an North to Beijing West.

I had taken the high-speed train between Xi’an and Beijing many times, except normally I took the earlier G672 service. But my clients had been such a pain today for some reason, so by the time I reached Xi’an North Station, the G672 train had already left.

“Everyone has to have a ticket.” The train attendant seemed a little angry, her eyes widening further as she glared.

“How did this happen? Do you all have some special express ticket then?” I raised my voice and looked around. But the other passengers all remained silent. Under the tangerine lamplight of the train carriage, a young man who looked to be a university student stared at his phone, head lowered; an old man wearing gold wire-framed glasses was reading a book, while a pot-bellied middle-aged man flicked through a thick photo album.

“They are all looking at their train tickets, I’ve already checked.” The corner of the train attendant’s mouth raised slightly and a small round dimple appeared beside her upper lip.

“Nonsense. They’re all just reading, aren’t they?” I lowered my voice, suddenly feeling a little strange—we were nearly at the station, so why was everyone reading still?

“Young man, don’t you have a … diary?” The bespectacled old man interjected leisurely, raising the book in his hands. Just then, I realised that it wasn’t a book—it was a diary with a plasticky leather cover. There was a papercut silhouette of the White Pagoda from Beihai Park on the red cover, and beneath it was a single word, so worn away that it was almost completely illegible: Diary. It looked just like the style that had been popular many years ago; I remembered having so many notebooks like that at home when I was little, with fine calligraphy inked in blue on each yellow page.

“What decade is this, who even keeps a diary anymore?” I was completely baffled.

“The diary is the train ticket.” The university student waved his phone in the air, “Blog posts count too.”

“Photographs are fine as well.” The middle-aged man’s voice was surprisingly soft as he spoke, “If you don’t have a train ticket, how are you going to change trains?”

“Change trains? I don’t need to change trains. Once we get to the station I’m going home.” I was getting quite angry now. What was happening today? All of the people on this train were so strange.

The other passengers didn’t respond, and the only sound was the drawn-out whistle of the train entering the station. I suddenly felt chilled. The train attendant shook her head, a strange light flashing in her round eyes.

“If you don’t have a train ticket, then there’s nothing to be done. Please leave the train immediately.”

“I was planning to get off here anyway.” I hurriedly grabbed my briefcase and strode out of the carriage, afraid the train attendant might change her mind.

The platform was dimly lit and the crowds of people seemed like one great black shadow, swaying and lurching in the cold wind. I turned up the collar of my coat and fastened the zipper, but it still felt like heat was gradually slipping out of the tiny gaps between the seams. I struggled through the crowd to the stairs that led to the station’s exit hall. I had to get home quickly; I still had a report to churn out this evening, ready for handing in to my boss before the meeting tomorrow morning …

The station gradually grew brighter and warmer. When I raised my head, all I could see in the chrome yellow lamplight were four large red words, ‘Beijing West Railway Station’, suspended high in the air in the centre of the hall.

Honestly! Clearly this was Beijing West Railway Station, so what sort of special train had they even been talking about? My steps grew softer as I thought back on what had just happened.

However, where the station exit and its cotton curtains should have been, there was now, somehow, a very small brass revolving door. A worker leaned against the wall beside it, arms folded.

When had West Station changed its layout? Or had I been too tired when I had been here last, only a few days ago, and I just remembered it all wrong? I blinked hard and stared around the hall.

The station exit was nowhere to be seen. Instead, identical brass revolving doors were densely packed all around the edges of the hall.

Beside each revolving door was a worker wearing a knitted vest, checking passengers tickets one by one.

I chose the line with the fewest people. A middle school student in front of me took out a small silver key and opened a locked diary with a click. My ears were ringing—wait a minute! Were they really … checking those special express tickets?

“Please show your ticket.” The ticket conductor was a tall, lanky young man and his shirt collar was turned out loosely over his knitted vest.

I gingerly produced my crumpled train ticket. He barked out a laugh, took my ticket in hand and tore it in two.

“You’ve got to be kidding.”

“I—I don’t have that kind of ticket.” I rummaged through the contents of my briefcase, but there was nothing there.

“I’m not trying to make things difficult for you, it’s just that without a train ticket, there’s nowhere you can go.” The ticket conductor moved aside and pushed at the revolving door. “Take a look for yourself.”

I looked out beyond the door and felt a sudden spell of vertigo. The square outside the station, normally so loud and full of people, was nowhere to be seen; a grey mist stretched out from within the endlessly rotating doors, silent and dark, seemingly leading to nothing but void.

What … was this place?

“Next.” The ticket conductor waved his hand. “You’ll just have to stay in the station for now.”

“Absolutely not! I want to go home!” I was getting anxious now and wanted to continue arguing with him, but I was pushed aside by the passenger behind me. The shadow-like streams of people surged to fill the gaps in the line, each person clasping train tickets of every description in their hands.

I suddenly understood why the train attendant had let me off the train so easily: she knew that even if I left the train, I had no way of leaving the station.

Damn it. What should I do? When I raised my head, the letters spelling out ‘Beijing West Railway Station’ were dazzling red. The train, then this train station, and now having skipped the fare – no, it wasn’t that I had skipped the fare … but still … of course! Even if I hadn’t bought a ticket, there must be a way to pay a late fare before leaving the station!

I turned around abruptly. Late fares, late fares—I remembered that Beijing West Railway Station’s late fare office was tucked away in a little corner of the third floor. Yet I still wasn’t sure if I could pay late for that kind of ticket there.

I pounded up the stairs. I don’t know if it was just because I was getting tired, but the stairs beneath my feet seemed just as long as they were steep. I finally reached the third floor; even as I tried frantically to find the sign for the ‘Passenger Services—Late Fares’ office, I was so exhausted that I could barely stand up straight.

I panted heavily as I knocked on the door, vaguely able to hear the sound of two people talking inside the office. “Is anyone there? I want to pay a late fare!”

“Come in!” came a woman’s voice, but when the door opened, an old man with white hair and a white beard walked out. He was wearing a long traditional robe, just like the ones in costume dramas, and he was muttering to himself in a language I couldn’t understand; yet it was what he carried against his chest that made me stare at him, wide-eyed.

A bundle of bamboo writing strips.

“What on earth are you standing there gawking for?” The person inside the room called out, voice raised.

I hurried inside and shut the door softly behind me. The office wasn’t big; an old-fashioned desk was buried amongst a mountain of paperwork, and behind the desk sat a plump older woman, her knitted vest stuffed full to bursting. Her hands were still busy working away at some knitting.

“I … I want to pay a late fare, for the G674 service …” I stammered. “I—I didn’t know it was a special train …”

“Took the wrong train?” The auntie set down her knitting needles and flicked through something in the pile of documents. “All right, early twenty-first century, that’s not too difficult. Come and sit down, young man.”

This auntie seemed much nicer than the train attendant from before. “Well, could I just ask you – this train station … what exactly is going on here?”

“Have you studied quantum mechanics before?”

“Eh?” I was a little confused. “That’s something to do with multiple universes … the observer effect and so on …”

“Not bad.” The auntie clicked her knitting needles together seriously. “This West Station here is the result of quantum polymorphism being amplified until it reaches macro-universe scale. ‘The past’ and ‘the future’ both consist of countless pre-existing tracks, and they all converge here. The only thing that can determine the trajectory of your world is your train ticket—observations of the past.”

“Who … who are you people?”

“We’re train station workers, of course.” She looked at me in confusion. “Ever since faster-than-lightspeed travel became more popular, more and more wormholes have been appearing between different worlds, so the role of train stations has developed in tandem. Look here.” She spread out the knitting in her hands. At first it seemed to be a wide shawl, and all across the indigo background, tiny dots were knitted with different coloured threads. Each dot radiated lots of little lines, some of which criss-crossed one another, and the gaps between them formed even smaller dots, until the whole piece had the appearance of a huge, dazzling net. “Beijing West Railway Station is the biggest station in Asia; the only one of comparable scale would be New York’s Central Station …”

“Wait a moment, are you saying that … every passenger here is travelling to a different universe …?”

“Yes. Depending on their ticket, they’re connected to a new world track.” She sighed, “Ah, it can be quite troublesome sometimes, like with that old man just now. He came along one of the old Han dynasty highways and his ticket was from sometime early in the first millennium, so changing tracks was really complicated …”

“The Han dynasty … is that possible?”

“It’s not anything too impressive.” She carried on knitting as she spoke, “History is nothing more than a complex construction of records and observations. How worlds are split apart, how they’re merged together, how they overlap – you have to knit a lot before you can understand. The most important thing in knitting is evenness. Right now, we have to rely on observational records. Each record is a stitch in a piece of knitting, where threads are brought together, where they diverge. Countless stitches determine the final form of a length of yarn, but at the same time, each stitch is part of countless lengths of yarn …”

“Then—then if I wanted to return to my original world, I would have to …” The auntie’s words were as hard to untangle as a ball of wool, but I felt that I understood what I had to do.

“You have to decide which were the important ‘stitches’ in your life, and then rewrite your diary.” The auntie used her knitting needles to point at an empty white notebook spread out on the desk. “Write in here.”

I took a deep breath, sat down before the desk, and picked up a pen. Covered by an emerald shade, the brass desk lamp emitted a soft light, reminding me of the libraries where I studied in the evenings as a university student. What really were the events over the past twenty or so years that had decided the trajectory of my world?

Six years old: The first time I received a birthday present, a mini 4x4 toy car. I was so excited that I took it apart and put it back together again over and over.

Twelve years old: The first time I visited Beijing with my family. I decided I would go to university in Beijing when I was older.

Fifteen years old: Entrance exams disrupted any semblance of normality, and I wasn’t able to go to my ideal high school. My first taste of failure.

Sixteen years old: My beloved grandmother died, but because I was preparing for exams, I didn’t go back home to the countryside to take part in her funeral procession.

Seventeen years old: I had a huge fight with my best friend. We unfriended each other on QQ and deleted each other’s numbers from our mobile phones.

Eighteen years old: Despite my family’s resistance, I chose to study a less popular degree subject.

I couldn’t write any more. It turned out that the trajectory of my world had been determined by the stitches of so many regrets. It turned out that I had had so many chances to enter into a new, potentially better world.

I remembered the ice-cold look on my boss’ face; remembered the small apartment that I rented with others; remembered all of the people and chances that I had let slip me by. I looked out the window to see a dense grey fog floating through the deep darkness of night. Somewhere below that mist, could there really be an ancient Han dynasty highway, or a high-speed train track from the twenty-first century, or countless tracks leading towards different worlds?

“Wait!” I suddenly realised something: that middle school student carrying a diary, the old man and his bamboo writing strips … “Are you saying that this train station can create different world tracks according to passengers’ tickets?”

The auntie nodded.

“So … Suppose then that what I wrote in my diary was different from the things that had already happened, the world—it would develop in a different direction, right?” I couldn’t suppress the quiver in my voice. “Those passengers … they—they’re actually here to change their worlds, right?”

“They’re not actually real changes.” The auntie continued knitting. “You’re only changing tracks. You still haven’t fully understood—you only know that the future is open, shifting, and that the past can’t be changed. But in fact, observational records that are used to restore the truth of a matter often point to multiple pasts, and these multiple pasts do not overlap easily. There isn’t one single past, but rather countless possibilities collected together. The train ticket is what allows all these countless possible pasts to collapse into one—”

“I can change this diary however I want, right?” I interrupted, staring at the auntie fixedly.

“Each ticket can only change one area. And only specific things that you have personally experienced or had direct contact with can be written into your diary.”

“One area … so—that man just now … the man from the Han dynasty, what did he change?”

“That in the battle he commanded in Kunming, the enemy wouldn’t use catapults to attack.” The auntie finally stopped knitting. “Look here, that counted as the one area that he could change. Don’t think of ending the world or anything like that, young man. Our workload is heavy enough as it is.”

One area. I didn’t have enough time to consider every period of history in detail. In my relatively short lifetime, what was the stitch that was actually worth changing, that would warrant entering an entirely new world?

“The size of the change doesn’t matter. Think about what you would regret if you didn’t change it.” The auntie's voice came to me as if from behind a layer of fog.

The thing I regretted most … I stared at the green lampshade. Under my gaze, the ball of light gradually grew larger, until it seemed exactly like something I had seen a very long time ago. And it had been in this kind of light that I had once gazed at a girl’s face, a tiny mole just beneath her eye …

But I had lost her. It had been another cold night back then, with thick fog filling the air, when I had sent that break-up message.

I didn’t hesitate any longer. I wrote down that day’s date, paused a moment, and then kept on writing that we had got back together again. The blue ink dried quickly on the yellow pages, soon looking as if it had been written a very, very long time ago.

When the ticket conductor stepped aside, I held the diary tightly to my chest and closed my eyes, then stepped into the brass revolving doors.

“What took you so long?”

I saw her as soon as I opened my eyes. She was waiting in the open square to the south of the station, a plastic bag clutched in her hands. Hot steam wafted from the top of the bag, bringing with it the scent of spring onions and eggs, made all the more enticing by the cold Beijing night air. That had been our favourite midnight snack as university students.

I embraced her tightly. That warm touch was somehow, inconceivably, real.

“Is it … really you?”

“What’s the matter? Ah … okay, let’s hurry home. The jianbing are getting cold.”

The story should end here, but time is just like an express train that drives on forever without rest—I had no chance to pause and look back, and was instead swept along by life, always surging onwards.

I never told anyone about that special express train, nor that special Beijing West Railway Station—I never even told her. I just began to keep a diary. Not just a leather-covered diary and a diary app on my phone—I even bought a digital camera, so that I could take lots of photographs on every important day and at every place I went to.

I never posted my diary entries or photographs on social media, either. I knew that the power they held was far greater than other people thought.

I also grew more and more interested in history. I found out later that even though his enemy hadn’t attacked with catapults, that old man from the Han dynasty had still suffered a crushing defeat in the end. Yet nonetheless, I still lost myself in ancient, unclear words, searching for that which had been forgotten or concealed—searching for another world. History is a complex construction of records and observations, and often in the deep quiet of night, I would imagine that somewhere amidst the long threads of time and space, countless possibilities were growing like vines, surging forth like so many streams, until eventually they all flowed into the void and that vast, unspeakable net at its centre.

I often took trains. In my pocket I always carried a diary, as well as my phone and an external hard drive. Yet I never took that special train again. I went to Beijing West Railway Station many more times too, yet the station lights weren’t ever that warm yellow colour, remaining instead ice-white and cold. I never saw any workers wearing knitted vests either.

As time went on, even I couldn’t be sure if that night had really happened or not. It became a secret that I kept with myself, and amidst the fog of uncertainty it slowly slipped away.

Until a long, long time later.

Once, after I fell into an unusually deep slumber, I returned once more to Beijing West Railway Station. By then, my hair was fully white and my hands trembled; such a peaceful sleep was rare indeed for the elderly. Perhaps because of this, the train attendant didn’t check my ticket.

As soon as I saw that chrome yellow lamplight and those brass revolving doors again, so many memories of the past suddenly came rushing back to life. My eyes, hidden beneath wrinkles, grew damp. It had all been real – it wasn’t a dream.

“Young man, you’re back.” Stood beside the revolving doors was the auntie in her knitted vest. Even though my daughter was already older than she was, still I knew that I would forever be that young man paying his late fare in her eyes.

“Seems like you’ve got your ticket all sorted this time. Where do you want to go?”

I took out my phone and diary. Over the past fifty years, I had kept a constant record of every stitch in my life. From investment choices and job changes, to my child’s birth and our medical records: I had kept a separate diary of every wavering possibility. My diary was not one single thread, but a whole net. I had lived on the borders of countless possibilities, waiting for this day to come.

But I was different now from when I was young: the present me had not yet decided which road I should take.

“I … want to ask, after I use the ticket to change tracks, the track from before … where does it go?”

The auntie laughed.

“You want to know? The track from before is still there. You can choose to move onto a new track, but there is another you on the old track forever.”

I nodded silently; it was just as I had long thought. The power of records was so immense that the worlds they created did not fade away. All of the joy I experienced on this track could perhaps on another track be unbearable suffering and torment.

Changing tracks could maybe help me to enjoy an altered past, but this was certainly not without cost. With the change of tracks, a little part of me had already left me forever.

That little part was enduring all that I should have endured, bearing all that I should have borne. Behind the sweet fruits of life were countless bitter branches. Yet it was also only through this bitterness that I, as an individual, could be a complete, real me.

Regardless of whether it was a garden where narrow paths diverge, or a train station where fate intersects; a confused tangle of conflicting versions of history, or the starting point of countless futures—even if there was no way to really understand the mysteries of parallel universes, still it had already had an incomparably profound impact on the way we thought about the world, and the way we thought about ourselves. It wasn’t a single shortcut that settled everything once and for all, but rather, it produced a feeling of vertigo just like Copernicus would have felt: if I am standing in a hall with mirrors all around, the me in each mirror can all loudly claim that they are the most important. And as for me—which one should I actually listen to?

Perhaps only Leibniz said it right: that out of all possible worlds, the world we are living in is the most beautiful one. His only mistake was in believing that such a world was unique.

I knew what I should do.

I deleted all the copies of my diary from my phone. I only kept the leather bound diary that had accompanied me for so long. That was the world in which the real me resided.

“This is my ticket.”

Once again, I stepped into those brass revolving doors—only this time, I kept my eyes open.

I knew that the person waiting for me outside the station was her, with hair just as white as mine. And although I was full of regrets, nonetheless I had lived an incomparably complete life.