In 2005, an alternate reality game asked players to find a man named Satoshi based just on a photograph. Fifteen years later, the mystery was solved.
A mystery cube a secret identity and a puzzle solved after 15 years

ON SUNDAY FEBRUARY 4, 2007, as the Sun rose over Wakerley Great Wood in Northamptonshire, Andy Darley trudged into the ancient forest with a map and a spade, and began to dig. The clock was ticking – others were closing in. Darley, a web designer from Middlesex, near London, had made three trips here in as many days. The previous night he had caught a glimpse of a torch in the darkness – if he didn’t find what he was looking for soon, someone else would.

He dug one hole after another. Nothing. It was getting light and he was running out of ideas. Darley sighed and looked at his feet. The surface of the ground beside him seemed different; the topsoil was mixed with clay. Someone had disturbed the earth in the recent past… or perhaps buried something? He dropped to his knees, grabbed a trowel and plunged the metal into the dirt. Six inches deep it struck a solid object. “That was when it hit me,” he recounted later on his website. “That was when I knew I’d found the Cube.”

Four days later, Darley walked into the office of Mind Candy, a gaming company based in London, to present his find and claim a £100,000 prize. Darley had reached the finish line of Perplex City, an alternate reality game launched in 2005 which saw 50,000 players embark on a scavenger hunt guided by a complex web of puzzles that blurred real and virtual worlds. Players navigated an immersive story while solving clues found in puzzle cards sold in shops, and in every form of media available: websites, live events, voicemails and text messages. It was a race to locate the “Receda Cube”, a spiritual artifact valuable to the residents of Perplex City, a fictional extraterrestrial society where puzzles – and the ability to crack them – are valued above all.

Darley won the game, but it was not complete. Not for players like Laura E Hall, then a student from Texas, who – while Darley scurried around in the darkness with a spade – kept track of the climax of the hunt for the Cube via forums and phone communication with members of her own Perplex City team. She too had someone on the ground in Wakerley Great Wood, digging holes. News that the Cube had been found spread like wildfire among the players. It was a grand finale that made headlines around the world, but those who had spent the last two years immersed in the Perplex City universe knew there was still work left to be done.

The game featured 256 puzzle cards, and while the main prize had been claimed, three remained to be cracked. One required players to prove the Riemann hypothesis, among history’s greatest unsolved maths problems, so a solution was not expected anytime soon. Then there was “The Thirteenth Labour”, a card with an encrypted message the designers estimated would take 30 thousand computers working in tandem months to unpick. So that was on the backburner too. The third card yet to be solved, card #256, was named “Billion to One”. It featured a photograph of a man with some Japanese text that read: “Find Me”.

For most, the discovery of the Cube concluded the game. But Hall was mesmerised by the unsolved puzzle card and the anonymous man staring back at her. For her, it had just begun.

HALL WAS MID-WAY through her studies at St Mary’s University, San Antonio, when she first heard about Perplex City. The game was promoted via a series of cryptic newspaper advertisements, mistaken by some for an MI5 recruitment drive, that asked for help locating a missing cube. When she spotted one circulating online, she signed up right away. She always loved a mystery. Speaking from her home in Portland, Oregon, Hall, now 35 with reddish-brown hair and clear-framed glasses, describes how she was raised on novels like Nancy Drew, about a teen detective, and Encyclopedia Brown, about, well, a ten-year-old detective. But it was The Eleventh Hour, a puzzle book by Graeme Base published in 1989, that “set her on that path”. Even today it is kept within reach – she disappears from the screen and returns moments later holding the colourful illustrated book, a story punctuated with secret ciphers and codes, between her hands.

“In the back there’s a sealed envelope with all the answers,” she says. “It’s still sealed.”

Why?

“Well, I still haven’t solved all the puzzles.”

Hall is what you could call a completist. She also appreciates how a good story can transform a puzzle into something transportative. Perplex City did just that. Like Alice in Wonderland meets The Matrix, it was conceived as a 21st century version of Masquerade, a puzzle book by Kit Williams that was published in 1979 and contained clues to the location of a golden hare buried somewhere in England. Two decades after Masquerade sparked a national frenzy, Perplex City used the architecture of the internet to construct not just a treasure hunt, but a parallel universe that was accessed via the computer screen. “The thing that drew me to these games, and the immersive genre more broadly, is that the potential for adventure is there, if you're willing to take the leap,” Hall says.

Hall took that leap. She found herself in a world that was rich, intricate and truly inter-dimensional. Playing Perplex City meant following a detailed plot – awash with murder and conspiracy – that unfolded in real-time across numerous sources woven with clues, much of which was crafted by lead writer Naomi Alderman, who went on to write novels including The Power. There was an online newspaper, The Sentinel, which players could contribute to; a record label, Hesh Records, that released an album; and “living” characters with active blogs. When one character, Violet Kiteway, asked players to write her a book, they published (and sold) an anthology called Tales from the Third Planet. When another, Anna Heath, was murdered, the players delivered 333 origami cranes to the Mind Candy office as a token of remembrance. Darley says he even shed a tear. The characters had personal email addresses too, though Hall was “always too shy” to write to them. Instead, she took a lead managing the player wiki – cataloguing information as the game progressed. Her personality at the time, she says, was “secret librarian”.

The puzzle cards – sold in packs – were how Mind Candy monetised the game. The cards were designed as standalone brainteasers, though some contained hints for the Cube hunt or details that brought players deeper into the Perplex City universe. The cards were ranked from red (easy) to silver (hardest). Solving them earned points that would notch players up a leaderboard, but really the competition was with themselves. Besides, many of the puzzles required a collaborative effort. A year into the game, the Billion to One card (silver, naturally) was released. Hall heard about it through the player community but didn’t see it in print until a friend sent her one some time later. The photo on the card was deliberately obtuse: a selfie of a man of Asian appearance with some European-looking, wooden-beamed houses behind him. The man in the photo is smiling, ever so slightly. One hint was provided: “My name is Satoshi”. Hall always believed it was possible to solve. “I had a feeling that it was more about the limitations of the internet,” she says.

The early noughties, when alternate reality games (ARGs) emerged, were a tipping point for internet culture. Social media as we know it was just taking off (even if that meant splurging on Livejournal or making your Myspace page rain sparkles), Web 2.0 was gathering pace, and the world was becoming intricately networked. By encouraging players to co-ordinate remotely to solve complex problems, these games challenged the possibilities of a connected world, but the first ARGs were used for headline-grabbing “transmedia” marketing campaigns. The Beast – widely considered to be the first ARG, though the term did not yet exist – was an immersive murder mystery created to promote the film A.I. Artificial Intelligence in 2001. Much like the “mind-game” films of the era, such as The GameMemento or Oldboy, ARGs toyed with multi-layered realities. “This is not a game” was a saying among players. Entry points were called “rabbit holes” and the writers were “puppet masters”. Combined with common themes of conspiracy, it’s hard not to view the moment as unsettlingly prophetic. In recent years, QAnon, a conspiracy theory in which a “puppet master” leaves cryptic messages on online forums, has been likened to ARGs. Adrian Hon, director of play at Mind Candy, who designed and produced Perplex City, recently wrote that the “parallels were striking”.

For Michael Acton Smith, the founder of Mind Candy, that time period was fertile for experimentation. Games like Perplex City were set to have “explosive” growth, he predicted at the time, but the concept never really took hold. “It was creatively one of the most extraordinary things I have worked on,” he says. “But commercially one of the most disastrous.” ARGs, Smith says, proved to be more of an art form than a commercial venture. After raising $10m in venture capital for Perplex City (and spending most of it), Smith cancelled the planned second season and used the remaining $1m to launch Moshi Monsters, an online world for children, which ran from 2008-2019. His latest product is the hugely successful meditation app Calm, which, when compared to Perplex City, perhaps suggests that more people want to zen out than spin out.

What Hall really remembers now is not the world of Perplex City, but the community. She’s a person who talks fondly about the “good internet” – a time before social media really took hold, when the web was still more of a trusting and optimistic place. “There was none of the dystopian stuff we have now,” she says. “Just the idea that all knowledge is accessible”. Through Perplex City she got to know archaeologists, city planners and all sorts of “clever, interesting people” whom she otherwise may not have met. It felt like the utopian ideals of the web were playing out around her. “What I found appealing about the internet was this flattening of access to people’s ideas.” she says. “I'm interested in the removal of distance between people. Geographically, culturally, or through time.” Hall really did believe that everyone was, in some way, connected. So the Billion to One card stuck out for her. There was no trick. It simply asked: how connected are we really?

THE IDEA THAT everyone in the world is joined by a few links, acquaintances or degrees has been bouncing around for a century. Frigyes Karinthy, the Hungarian writer, mooted the idea in a short story called Chains in 1929, in which the characters play a game to prove that anyone in the world – be it a Nobel prize winner or a riveter at the Ford factory – can be reached via five intermediaries. “Let me put it this way,” he wrote. “Planet Earth has never been as tiny as it is now.”

The “small world” phenomenon was famously tested in the 1960s by Stanley Milgram, who asked people to deliver a letter to a target. If they knew the target, great, he told them, send it right on. If not, the subject had to deliver the letter to an acquaintance who was closer to the target – and ask them to repeat the process until it reached the destination. Of the letters that reached their target, the average length of the chain of people was six. The methodology may have been imperfect, but it captured the imagination. The phrase “six degrees of separation” came from John Guare’s play of the same name, which hit broadway in 1991. Soon after, the idea became a pop culture phenomenon, with Kevin Bacon, the unwitting star of a parlour game in which players linked Hollywood actors to him, at the heart of it. One of the first social networks was SixDegrees.com. Every day, online, we indulge our fascination with the idea that everyone is just a click away.

Duncan Watts, a network theorist and author of Six Degrees: The Science of a Connected Age, followed up on Milgram’s work in 2003 with a study that tracked thousands of email chains. The median number of links for a correspondence to reach its target was still between five and seven. Consequent studies found a similar range. “But just because you can theoretically connect to anybody in the world through a short link,” Watts says, “doesn't mean that you can do it in practice.” The internet has not significantly reduced the number of degrees between us, but it has certainly nurtured the idea that we are closer; our ability to communicate has become “supercharged”, Watts says, and the networks available to us are more visible than ever. Connectedness, however, is a double-edged sword. As Watts has written: “In a world spanned by only six degrees, what goes around comes around faster than you think.”

The team at Mind Candy had no idea whether the Billion to One card would be solved by a chain of connections, or whether the search would be leapfrogged by technology. After all, no-one actually communicates in the way that Milgram prescribed. When we try to locate someone – or share an idea – we post, share, and make use of “hubs”: highly connected points in a network, like Google or Facebook, which the internet has made so accessible to us. Mind Candy’s Hon (who had no idea who Satoshi was) describes the Billion to One card as being about “collaborative detective work”. “To me that was the joy of making Perplex City,” he says. “The best puzzles are ones that really harnessed the collective power of the internet.”

Armed with a photo and a name, the Perplex City community threw itself into the hunt. “I felt very much that if this person was findable online, that we would do it,” Hall says. Today it might take one viral tweet, but in 2006 Twitter had barely hatched, Reddit had just enjoyed its first cake day, and Facebook had only recently expanded beyond schools and universities. To get the word out, one player, Chris Warren, built a website, billion2one.com. Hall set one up too, and printed out a bumper sticker with the URL on it. Perhaps, she thought, someone driving behind her would visit findsatoshi.com and recognise the man.

On the Unfiction forum, where ARG players gather, the hive mind whirred into motion. Frantic Googling soon revealed Satoshi to be an incredibly common name. Messages were sent to friends in Japan. One player spoke to someone at the Japan Times, “who said something I didn't understand.” Another wondered: “Is he a Disney Tokyo cast member?” One breakthrough was made. The players established that the architecture in the photo was indeed European – not Japanese – and confirmed the location as Kaysersberg, a small town in the Alsace region of France. One player posted: “Nice excuse for a little summer trip to Alsace, anyone?”

The following year, news broke that Darley had found the Cube. It was a satisfying moment. “The missing Cube was the whole point of this story,” Hall says. “It was the big MacGuffin.” But, for her at least, it was not the biggest MacGuffin. Hall was not prepared to give up on Satoshi. Other players supported the hunt too. Darley pledged £500 of his prize money to those in the chain that led to Satoshi, which was looked after by Warren, but as the months passed, the search lost momentum. Hall knew it needed more attention. She secured coverage from the Guardian and the New York Times. ABC even did a television piece on it.

In December 2007, Hall visited France for a company summit, one town over from Kaysersberg. “It felt a little fate-driven to me,” she says. Of course, she took the opportunity to visit. Kaysersberg is a dainty, postcard-perfect jumble of medieval architecture clustered around a river: tourists come for the photo-opp and stay for the wine. Hall navigated her way to the waterside and found herself standing on the exact same spot as Satoshi. She wasn’t closer to solving the puzzle, but doing something tangible – taking the search into the real world – felt meaningful. She took a selfie and made a gif that faded between the photo of Satoshi and herself. “Finding him always felt so close,” she says. “The best way I can describe it is like feeling that you would turn a corner and run into this person… but online.”

Hall’s pursuit of Satoshi was ongoing, but her attention had drifted to another kind of connection. She’d started a correspondence with Jey Biddulph, a designer at Mind Candy who joined the company as an intern straight out of sixth form college and never left. The pair had met a year earlier, in 2006, at a live event for Perplex City players in San Francisco. Technically they’d met already without realising: there’s a photo of Hall looking over Biddulph’s shoulder at an earlier event held in London. But San Francisco was when they were first properly introduced. Hall and Biddulph got chatting. Or rather, they performed a drunken karaoke duet to “Under the Sea” from The Little Mermaid. The instant they returned home, on separate sides of the Atlantic, the conversation continued online.

Soon the pair were in a long-distance relationship, “completely made possible” by technology. They hung out on Skype all day, “just to inhabit the same space”. When Hall was going to sleep, she could catch Biddulph waking up. They kept as synchronised as possible: they clicked play together when they watched films, and when their screens slowly drifted out of time, they realised that US and UK DVDs run at different frame rates. When the relationship reached that point “where you either break up or move in together”, Biddulph packed his bags and headed to the US to be with Hall. In 2009, he joined her in Texas and they married a few months later. The following year, they moved to Portland.

But there was another link between the couple; one they didn’t discover for a while. Biddulph knew who Satoshi was. In fact, he had personally designed the Billion to One card. Biddulph says it’s hard to recall exactly when it came up in conversation, but it was probably about a year or so into the relationship. “I think I just mentioned it at random one day,” he says. “And she was like, 'Uhh, what!?'”

Hall’s reaction was consistent with her life-long approach to puzzle-solving: “I made him promise to never, ever tell,” she says. “Because if he just came out and revealed it, all of that work would have been for nothing.” Biddulph respected the promise. “I bit my tongue for years,” he says. There was no teasing either. “He knew it was important to me,” says Hall. “I think he enjoyed being mysterious about it, too.”

Biddulph notwithstanding, it was around this time that Hall may have come within a close person-to-person connection with Satoshi. She received lots of tips via her website over the years. Mostly these weren’t much use, just dead-end leads, spoof messages or a photo of a random Asian guy found on Google images. But one tip stood out.

Subject: He's in Japan

My coworker used to live with Satoshi. She even brought an old photo of him to work today. Anyway, she said she does not know how to reach him, but that he is definitely in Japan right now, that he was in L.A. about three months ago.

I hope this helps.

“It was anon so it might have been BS,” says Hall, “but it just seemed genuine”. Hall responded but never received a reply. Years later, in 2011, the tip was still on her mind. She sent another follow up. This time, a response: “I quit the job five years ago, so I don't think I'll be able to help you. Good luck.”

Despite her resolution to work things out for herself, when she received a good tip, Hall mentioned it to Biddulph and scanned him for tells. “Normally he’d be completely stone faced with no reaction,” she said. “But this was the only time he reacted. It was so subtle, subconscious even.” She adds: “That was the most confirmation I wanted or could get. To think I was so close… that did feel like sand slipping through my fingers.” The trail went cold.


THE HUNT FOR Satoshi was not advancing. But technology was. The first cryptocurrency was founded, and Googling Satoshi now churned up results about Satoshi Nakamoto, the creator of Bitcoin. Some posited that the two were somehow connected (they were not). Smartphones were now in the pockets of millions. By 2010, Facebook and YouTube each had around half a billion users. Instagram had launched. A Perplex City player, going by Paraboloid13, actually cracked the cipher on the “Thirteenth Labour” card, according to reports from the community. Social media networks – and the memes that flurried through them – fuelled political movements from the Arab Spring to uprisings in Hong Kong. By the end of the decade, Facebook had 2.3 billion users and even TikTok, a relative newcomer, was pushing 1 billion. The “good internet” Hall fondly remembers was giving way to something more conflicted. Social media provided data for commercial and political interests. Algorithms moulded culture and society. People were falling down rabbit holes, and this time it really wasn’t a game. Occasionally the Perplex City community would discuss Satoshi, or Hall’s website would receive a spike of interest thanks to a blog or a podcast, but for many years, the search was forgotten.

Then, in February 2020, as the coronavirus pandemic crept from person to person around the world, Inside a Mind, a YouTube channel with more than 600,000 followers, posted a video about the hunt for Satoshi. “Can You Find This Man” generated hundreds of thousands of views in a short space of time. The world went into lockdown. People had time on their hands. Spurred on by the video, and completely separate to Hall’s search, a Reddit and Discord group were set up. Suddenly hundreds of people – many of whom had nothing to do with the original Perplex City game – were passionately working to track down Satoshi. As Albert-László Barabási, a professor of network science and author of Linked: The New Science of Networks, puts it: “When a hub gets infected, there’s a dramatic change in the system”.

It was a generation with a different relationship to the internet. “At first people asked if it was a conspiracy theory,” Hall says. “People wanted to know if it was legitimate, if something sinister was involved, or if we were trying to stalk this person.” Others asked if they could analyse the photo, and Hall had to explain that it originated as a printed photograph on a piece of card. Hall had grown up with an internet before deepfakes and computer-generated faces. “It seemed that people’s trust had decayed,” she says. “People’s trust to believe what they were seeing and presented with.”

Biddulph was uneasy about the renewed attention. When he designed the Billion to One card, the idea of finding one another via the web was still a thrill. Now the internet was fraught with issues of privacy. “Would I even be able to find someone to agree to have their face plastered on a puzzle with the explicit instruction to find them?” he says. “Maybe, but I reckon it'd take a lot more convincing.” He was unsure that new seekers would adhere to the same sorts of boundaries that were enforced among ARG communities, to stop people digging up private information. “Besides, Satoshi agreed a long time ago to do this, and I hadn't had any contact with him since that day,” he says. “How comfortable would he be with someone turning up and confronting him?”

Hall made an effort to temper the hive mind. She wanted to avoid anyone receiving a barrage of emails from strangers over something they knew nothing about. “It is overall a game,” she says. “But this part of it is just a person. These are real people, right? They're not fictional characters.” Hall asked to be a touch point to contact potential leads. Then, she sat back and waited: new networks were lighting up.

ON AUGUST 18, 2007, Talisa Säger, aged 12, stood on the deck of the ferry running from the small island of Föhr, in northwest Germany, to the mainland, and dropped a bottle into the North Sea. In it there was a letter. She’d always liked sending messages in bottles and chain letters – it felt adventurous. Sometimes she burned the edges of the paper to make it look older. She always hoped to receive a reply.

In December 2020, Säger arrived at her parent’s home in Hamburg to celebrate Christmas (and her 26th birthday). There was a letter waiting. She opened the envelope, pulled out the paper inside and began to read. Her message-in-a-bottle had been found – then lost for years – then found again. Now, finally, a reply. “I wish you all the love in the world and a wonderful birthday and a peaceful Christmas,” it read. “Isn’t this a great present? Especially in this corona-crazy time.” Säger was overwhelmed. “It felt unreal,” she says.

That evening, the Säger family talked about the unlikely connection that had been made. It sparked a memory for Talisa’s brother, Tom-Lucas. He recounted a story he’d stumbled across online: a YouTube video about a quest to find an anonymous man named Satoshi. Later, Tom-Lucas logged onto Reddit and discovered the search for Satoshi was still underway.

Tom-Lucas is an interaction designer who has conducted research into artificial intelligence. Through this work, he had encountered new facial recognition tools that allowed users to upload a photo of their face and find other photos of them across the internet. Tom-Lucas believes it is important people are aware of these tools. “A lot of people on the Reddit group were shocked you can find someone online using their facial features,” he says. “We need to find ways to regulate these things.”

The tool he used was provided by PimEyes, a Polish startup. A similar service, Clearview AI, is used by law enforcement agencies; PimEyes offers it to the masses. It is offered as a privacy service – a means to trace your own image – but Big Brother Watch, a civil liberties group, told the BBC it could “enable state surveillance, commercial monitoring and even stalking on a scale previously unimaginable”. PimEyes says it is “designed to find photos of the person who is conducting the search, not of other people.” But there is nothing to prevent someone scouring the web for someone else’s image. Which is exactly what Tom-Lucas did. He uploaded a photo of Satoshi and clicked search.

The top three results were the same old images of Satoshi, but the fourth was different. It was a photo of ten people smiling and making the peace sign. On the far right was a man wearing a T-shirt for a Swiss jazz festival and raising a glass of beer to the sky. He looked like Satoshi. The photo was indexed from 2018 – so it could not have been found before that – and the URL led to a Japanese company. Tom-Lucas posted his find on the subreddit, and soon after Hall received an email telling her to check the group – this was a lead worth pursuing.

Hall took a close look at the photo. Over the years she’d established ways to match a face, checking for things that don’t change so much over time, like skin marks or the shape of someone’s ear lobes: “I was like, these are the freckles… these are his actual facial markings.” A scout of the company website led to a possible email address. Hall asked a friend from Japan to phone the office, explain the search and leave her contact details. During the call, the office confirmed the man’s work email, so Hall had a message translated in Japanese and sent it directly. “I have been trying to solve this puzzle for 14 years,” she wrote. “And hope that you might be able to help me! Today, I am writing to ask a question: are you the man in this photograph?”


BEFORE THE BILLION to One card was created, the person on it could have been anyone. Biddulph almost selected someone from Ecuador. In the end, Satoshi was chosen. He was contacted by a friend and former colleague from a PR company that worked with Mind Candy and asked if he wanted to take part. “Why not!” he replied. He sent over a holiday snap – a selfie from a work trip to Europe. Satoshi had a question to relay to the person who found him, a piece of trivia about Japanese mythology: Who died after giving birth to flames? The answer was the solution to the puzzle card (can you figure it out?). Satoshi didn’t hear anything more about the game, or even see the Billion to One card. Soon he’d forgotten all about it. Fourteen years later, his company received a phone call.

Satoshi – or rather, Satoshi Shimojima, 49, from Nagano, Japan – is, in his own words, a “typical, ordinary Japanese man”. That was always sort of the point. “I anticipated it might be hard to find me,” he says, laughing. Speaking on Zoom, wearing a white shirt and a brown striped tie, Shimojima has a warm demeanour. He is now an executive at a car parts manufacturer, but he still likes gaming – when we speak he’s trying to get hold of a Playstation 5. He has a wife and two children. He likes golf and running (members of the r/FindSatoshi subreddit had already established he was a runner, after tracking his attendance at a marathon event). He smiles and touches his chin with his thumb thoughtfully as he recounts the moment he was found. When he heard his office had received a phone call – something about a man with a resemblance to someone in a photo – he was concerned. He thought it was some sort of scam. Then he remembered. He never dreamed anyone was still looking for him. Soon after, he received the email from Hall. “You can find more information at the website, findsatoshi.com,” she wrote.

Found Satoshi visited FindSatoshi.com. He read about the search. He found his photo on YouTube, Facebook and Reddit. He read the threads and conversations and forums. It was an uncanny experience, but as he read, he gradually felt reassured. The discussions were friendly, amicable – people were having fun. He could see the community wanted it to be a safe environment for him. “Laura had said that people should not violate my privacy,” he says. “And people respected that.” Smiling, he typed his reply, although he had long forgotten the riddle he was supposed to relay.

Hello,
Thank you for contacting me. You said you have been looking for the guy named Satoshi. I am Satoshi,,,,,,,,,
YES! 
I am Satoshi, who you have been looking for!!!


THE FEELING OF completion, Hall says, was “not fireworks”. It was a more prolonged feeling of satisfaction. “It was… balmy,” she says. “Soothing.” It took a while to dawn on her that it was done. Finally, Hall and Biddulph could sit down together and talk freely about the puzzle. Biddulph shared the creation process – he even dug up his old laptop to find the original emails with Shimojima. Hall and Shimojima stayed in touch. He said that if she was ever in Japan, she should visit.

Hall was pleased that the card was solved through the collective efforts of online communities. It reinforced her fundamental belief that the internet can be a unifying force, but the way the online landscape has evolved since the search began left a bittersweet feeling. The same tools, networks and hubs that helped find Satoshi have re-shaped society in ways that could not have been imagined when his photograph was first put on a card. Hall talks passionately about the way the US is being divided by conspiracy theories; after pursuing a mystery online for so long, she understands the allure of the idea that everything is verifiable on the internet, that answers lie “just one step out of reach.”

The hubs and chatter of the Perplex City community are now mostly buried beneath new strata of the web. The fabric of that fictional universe, once formed of countless sites, now consists of dead links and error messages. The Unfiction forum, which also received a donation from Darley to help sustain it, was archived in 2018. Warren kept the Satoshi prize fund "squirrelled away" – in January he divided it between Hall and Tom, who gave it to charities. For some players it was difficult to fully depart from Perplex City. Many stayed in touch. Some wrote fan fiction, weaving new narratives for the characters. When Darley found the Cube, he lifted the veil on that fictional reality but took four days to hand it in. There were practical reasons for this, but he admits a small part may have been an unwillingness to leave that world behind. “Good storytellers create worlds people don't want to leave,” he says. “And that was a good story.”

The hunt for Satoshi kept Hall connected to Perplex City for 14 years. “These games can be a deep, intense experience, and depending on how into them you get, it can take up a lot of time,” she says. “At that time in my life, I was able to dedicate a lot of time and energy to a game in that way, but that's changed as I've gotten older.” Now, she spends more time making puzzles for other people: she works as a games and escape room designer.

It’s an artform she thinks deeply about. A good puzzle leads people on an emotional journey, she says: “There’s a point to it.” With the Billion to One card, our interconnectedness proved to be the real puzzle, and each one of us a tiny piece. “No choice that we make is independent of anything or anybody,” Hall says. Puzzles, she adds, are a way of “staying deeply, creatively engaged with the world.” Sometimes they can layer new meaning over it. Sometimes they simply help you see it the way it is.