In the middle of a forest, just before midnight, I stare up at a homemade lamppost. Rising from the foliage and snow-spotted terrain, it stands unlit in the brisk autumn air. Fifteen other people are with me, craning their necks upward, oohing and aahing. One approaches the Narnia-esque discovery, opens a circular door in its black plastic piping and fiddles with the post’s inner workings. Suddenly, the lamp flashes. “Turn off your lights,” someone barks, and the sea of headlamps and handhelds cuts out. Above us, on a clear plastic panel jutting from the post, numbers blink one by one against the bare branches and starry sky. What’s left of the magical C.S. Lewis aura is gone. We’re geocaching, and these are our coordinates.   

Like a gang of smartphone-obsessed teenagers at a party, we stand in a huddle, staring at our Global Positioning System devices as we input the numbers carefully; one wrong digit could send us kilometres in the wrong direction. After a symphony of beeps, we have the location of our next cache. We leave the lamppost, bushwhacking through swampy wilderness and dense undergrowth, and find an ammunition box with a logbook inside. We sign our names: Draelynx, stinger503, missbug and so on. Like hackers and gamers, geocachers have alternate online identities—it’s just that their territory is the real world.  

Geocaching, a twenty-first-century game of X-marks-the-spot, has all the adventure of The Legend of Zelda, but with the thrill of scaling an actual mountain. It’s thrown a generation of technophiles offline and into the forest. The call of the wild beckons, and geocachers—with a GPS device in one hand and an iPhone in the other—have answered.

The first geocache—planted by an Oregon computer consultant named Dave Ulmer—dates back to May 3, 2000, a day after the United States government made accurate GPS data available to the public. (GPS works through trilateration: a GPS device measures its proximity to four or more government satellites, then determines its location based on where the distances from each satellite intersect.) Ulmer hid a cache—a bucket that held two CDs, a cassette recorder and a George of the Jungle VHS tape, among other items—and posted its coordinates online, along with an early draft of the game’s rules and a prediction that there would, one day, be thousands of caches all over the world.

He underestimated. The game caught on via online forums, and others soon began hiding their own caches—mostly Tupperware containers, film canisters and pill bottles—in both urban and rural environments. Within six months, there were seventy-five known geocaches and a website to help would-be cachers find them. Today, now that GPS-enabled smartphones and a geocaching app have made the game even more accessible, there are two million caches—including one at the summit of Mount Everest and another in the International Space Station—and more than five million cachers in 160 countries.

At the moment, as the sun sets, several dozen such cachers are scattered around an unusually busy Milton, Ontario pub. One stands at the front of the restaurant, selling reflective tacks and discussing the difference between short- and long-wave ultraviolet light. Another watches the door, pointing out high-profile cachers as they arrive. And Gregory Pleau, the crew’s unofficial leader, is lugging around a camera with a two-pound lens, snapping photos. Tonight is Boot Camp, an annual overnight caching event organized by a group of Greater Toronto Area cachers who call themselves the Keepers of the Order of the Big Flashlight, or BFL.

The typical Friday-night outing for the BFL is a less elaborate, four-hour affair bookended by trips to the local Tim Hortons, with a dozen cachers at most. But for Boot Camp, Pleau and a handful of others have spent endless hours and hundreds of dollars scouting the terrain of Halton Region and planting caches.

At 7:58 pm, when Pleau takes the stage, dozens of cachers have already begun crowding the front of the pub, itching to hit the trails. Decked in winter jackets, hiking boots and ski gloves, they look like a mosh pit of outdoorsmen fresh from a trip to Mountain Equipment Co-op. On a table in front of them sit three piles of paper: maps, lists of the caches and sheets of tortuously intricate math calculations—what the BFL crew has taken to calling the “tax-return form.”

When combined with information hidden inside a series of seven smaller caches, it will reveal the location of the final find. At 8:03, Pleau gives the go-ahead, the group swarms the table and, within minutes, the pub is virtually empty.

By 8:30—a few hours before the lamppost episode—two dozen of us have driven into the woods, following one of the seven pairs of coordinates. We hunch over an ammo box as an eager cacher flips switches and repeatedly pushes a red button on a homemade puzzle, trying to get a screen to light up with a new set of numbers that will point us in the right direction. “You know where would be a great place for this?” someone asks. “In the middle of an intersection in downtown Toronto.” It wouldn’t be the first time. In May 2012, police mistook a geocache in west Toronto for a pipe bomb, tying up emergency services for hours; the same thing happened in Ottawa in 2008. When we follow our latest coordinates, however, we find the usual, non-lethal prizes: a logbook, a voucher for a prize of our choice (like a laser pointer or cat-patterned socks) and a number to plug into our tax-return form. But we take nothing and leave nothing. Geocachers are more concerned with the hunt than the reward.

That hunt has led us deep into the woods, where we scour an overgrown ruin in search of our next cache. If you ignore the graffiti, the setting—crumbling stone walls next to a tall cement structure that resembles a grain silo or a watchtower—feels like the site of a medieval battle (though, more likely, it’s the remnants of a nearby quarry). Fittingly, this scenic cache was arranged by Pleau, the photographer. “Most of the early geocaches were placed in interesting areas: a waterfall nobody knew about in the woods, an old ruin,” he says. “They were secret spots that tended to be photogenic.” As we scour a nearby cavern for Pleau’s hidden treasure, a half-dozen cachers have their smartphones out, taking pictures of the search.

Depending on the setting and weather, BFL can also stand for a Bunch of Floating or Fucking Lunatics. Right now, the F stands for Frozen. Just past 2 am, our group is shivering under a canopy tent, our shoulders hunched against our ears and our hands wrapped around Styrofoam cups of hot chocolate. We flock to a barbecue, where one of the cache planters is cooking sausages. This is the command centre. Here, the masterminds behind the evening’s caches get to relax around a propane-fuelled fire, taking angry calls from confused cachers and ecstatic compliments from contented ones.

In the woods, Pleau is in his element: in the eight years since he co-founded the BFL, he’s spent almost every Friday night out in the bush of southern Ontario searching for caches. He founded the Toronto Area Geocachers and served as vice-president of the Ontario Geocaching Association, which helped encourage Parks Canada to shift from a ban on geocaching to hosting its own events. He’s already run six of these Boot Camps, and his caching pseudonym, northernpenguin, is practically a household name among enthusiasts. The folding chair he’s sitting on, for at least one night, is a kind of throne.

But without geocaching, he’d be no king. Although Pleau has always loved the outdoors, the game is what gets him out from behind his desk. “I lived in the city. I worked with computers,” he says. “The things I found interesting were cell phones and videogame systems.” He’s kilometres from the nearest Wi-Fi hotspot, but he’s likely spent the night discussing operating systems and swapping nightmarish stories of being an IT professional. After all, the crew is composed of geeks and techno-junkies like Pleau: an electronics marketer mans the barbecue; a Humber College technician prepares the hot chocolate. John Robb, who’s selling batteries, registered his first web domain in 1996, when less than two-thirds of a percent of the globe even had internet access.

At 3 am, Robb joins the seven remaining members of our group as we leave the command centre to find his cache. When we arrive at the coordinates, we flood the forest with light, looking for anything unusual, and find a test tube hanging from a tree branch. One of us points a laser at it and it blinks back in response—a sequence of red flashes giving us our next coordinates. Eventually, we uncover and open another ammo box, and from a small speaker under the lid—a repurposed record-your-own-message Hallmark card—we’re serenaded with a tinny rendition of “Blinded by the Light.”

Robb looks on, smiling. It’s nearly four in the morning, but this is where he wants to be. “I’m in front of a computer all day, sitting in an office under fluorescent light. That’s the way the world is now, but that’s not what our bodies are built for,” he says. “When I’m walking through the woods and I can smell the leaves on the ground and the sun is streaming through the trees—this is what we’re supposed to do.”

The canopy tent is long gone, most of the BFL crew is asleep and Boot Camp is over. But at 6 am, standing at the final coordinates, our group continues its search. We’ve found the seven smaller caches, along with the clues that led us here, and we’re hopeful that we’ll be the first to discover the final cache. Apart from the telltale traces of a bush party—empty beer bottles, plastic wrappers and rusted tin cans—there’s nothing to indicate any rival cachers have been here before us.

After fifteen minutes of searching—enough to make us wonder if we botched the cosine calculation or decimal-binary conversion on our now-complete tax-return form—we find a Sudoku puzzle hidden in a plastic container within a rocky fissure. But there are no numbers. Someone instinctively shines an ultraviolet light on the puzzle and the missing digits appear, along with a set of letters that, when the puzzle is solved, leads us to our final destination.

We descend a snow-covered slope, comparing GPS readings as we near the last cache. “I’ve got 15 metres,” one of us says. Fifteen becomes ten, ten becomes five, and then, nestled in the hollow of a tree, we find a golden ammo box. We pull it out, smiling and shaking like kids on Christmas morning. Inside, there’s a carefully folded Ziploc bag, wrapped around a yellow notebook. At 6:39 am, as the sun begins to inch over the horizon, we flip the notebook’s cover open to find a blank white page.