The light from our alien tracking devices jumps over the trees and stones in front of us. We know that the aliens are here somewhere, but where? The sky is clear and the moon shines down over Howarth Park. "Ding, ding," beeps the GPS device, announcing that we are at our destination. The coordinates should mark the beginning of a trail of reflective alien blood. Earlier, we received a tip that if we follow the residue it will lead us to a crashed alien ship that has landed in the park. This is the cache we are after.Unlike such traditional treasure-hunting activities as exploring the park with a metal detector, this is geocaching, a hide-and-seek game in which "treasure" is hidden in parks, parking lots, under lakes, in trees, in fence posts and in infinite other locations all over the world—all of it just waiting to be found, logged, admired and replaced.It all began on May 2, 2000, when 24 satellites around the globe updated, making GPS technology better than ever. Location hunting suddenly became easy, accessible and accurate.

On this night, the GPS device is in my brother Jeff's hand. Jeff likes to be known as the Cubemaster because he leaves a cube-shaped object as a calling card in the caches he finds. He looks down at the GPS and confirms we are in the right spot. Reflective shining alien blood must be here. Our buddy Kubo adjusts the lamp that he slid over his brow and tilts his head up toward the trees. John dances light of the crank lamp over stones that lay to the side of the path. Nothing yet. We start to walk down a dark clearing, Marshall eerily plays the X-Files theme song from his phone.

On May 4, 2002, near Beaver Creek, Ore., computer consultant Dave Ulmer held a black bucket rattling with treasure: a logbook, a pencil, videos, books, software and a slingshot. He hid the stash, noted the coordinates and posted them online to test the new accuracy of GPS devices. Thus began what was then known as "The Great American GPS Stash Hunt."As with anything niche and cool, the game was discriminating—only those with the knowledge of fancy GPS lingo or those who even had GPS devices, such as serious backpackers, could play.Web designer Jeremy Irish stumbled on to the game and was stoked when he found his first cache. Enthusiastically, he created Groundspeak.com, where all the cache listings were eventually standardized, a search for local caches was listed, and GPS slang was put into language that everyone could understand. By that September, a new world of geocaching was born. The "Great American GPS Stash Hunt" became the "GPS Stash Hunt" before adopting its current name, "geocaching," an amalgam of "geo" meaning "earth," reflecting the game as a global activity, and "cache," the French word meaning "a hiding place used for storage" (and the computer term for storing information).With the advent of Groundspeak, players started hiding more and more caches, and the number of them grew quickly around the world. Seven years later, there are some 842,433 caches in the world, a number that grows daily.

Each geocache has a different name ("Strolling for Trolls," "Lizards with Light Sabers," "Pigs and Goats and Elephants . . . Oh My!"), a different story behind it and a different treasure inside, which makes it unique and surprising to find. According to the populist rules outlined on Groundspeak, at bare minimum there must be a container and a logbook where geocachers can log their finds and post their experience on the website. Items vary with each cache, from small toys to postcards to golf balls. If you decide to take treasure as a souvenir, you must leave something else in its place (unless otherwise specified for a particular cache). And finally, you must log your name in the logbook and share your find on Groundspeak so others can see when it was last found.

We read about "Alien Nights," the geocache we are after, on Groundspeak before heading out. It is a mystery cache, meaning that the cache involves a puzzle we need to solve before we can find the treasure, in this instance a "tip" from Professor Simon Roswell of the SETI Institute in Washington, D.C., who claims to have uncovered evidence of an alien presence along the foot trails of Howarth Park. All we know is that we have to wait until dark to find it so we can use our alien tracking devices (flashlights) to find reflective material—alien blood.

The woods are dark but the sky is clear. No sign of the aliens. We continue walking. The Cubemaster slows down and shines his flashlight on the ground. "Hey, check this out." Tinsel. Alien blood? A yard ahead, more tinsel hangs from a branch. Another piece is shadowed under a rock. Excitedly, we keep moving forward. However, the tinsel seems to have stopped. We look everywhere, but no sign of more tinsel or the cache. We backtrack so as not to get discouraged. Cube rechecks the GPS. "Hmmm, we are at the right spot," he says. "It says here that someone found the cache a week ago."

Mark "Psychofish" Cook, 51, an avid geocacher, remembers setting flowers down on his mother's burial plot in September 2005 when he noticed a small ammo box. "This is weird," he thought. "Maybe some hunter put it here." He curiously opened the box; inside were toys, a logbook and a piece of paper with the Groundspeak website and an explanation of the game on it. Cook, who was always interested in maps and had always wanted a GPS, now had the excuse to get one.Four years later, he has found approximately 13,000 caches all over California, some in New Jersey, Pennsylvania and Kansas. He has also hidden 87 of his own. "I love the hunt and the outdoors," Cook says. The sport brings people together and gets them outside and moving. "I enjoy going out with my brother and my son, Ben, people I enjoy being with," he explains. Caches are everywhere, a truth that changes the perception of the environment. The game has "made me more observant," Cook says, "I have to notice things the average person doesn't see. I have to notice things a little bit more and it makes me more aware."The tinsel leads nowhere. "Let's see what other caches are around here and maybe we will find the alien blood as we look for some others," I suggest. The Cube checks his GPS, which is loaded with cache locations. "Frog Hideaway" and "Rocky Road" are nearby. With new coordinates, we wander a winding, tree-canopied path. We are looking for "Rocky Road." "Ding, ding," chimes the GPS. We are at the spot. To the right of where we are standing is a group of large rocks, which we all start scurrying over and climbing. We turn over the ones we can lift and carefully look under, around and in between the ones we cannot. This has to be the right spot.I crouch down on the ground; it is dark. I feel under the rocks with my hand. There is a small opening between where the stone and the dusty ground meet. I feel dirt on my fingertips, small pebbles, then something bigger. "Hey, quick! I need a flashlight!" Kubo runs over, rips off his headlamp and hands it to me. Everyone gathers around. I shine the light where my hand was. Under the stone is a small tube that is covered in camouflage duct tape. Eagerly, I open it. Inside is a yellow and black toy Datsun, a fake tattoo, a wobbly rubber skeleton, a button and a small address book used as the log book. Treasure!

Exhilarated by our find, we are ready to search for a new one. The Cubemaster plugs in the coordinates for "Frog Hideaway." To get there, we head up a steep hill. John moves branches out of the way so we can easily pass by them.

"Ding, ding." There is a clearing to the left and another grouping of rocks. These rocks are blanketed in moss, dried and damp leaves. If I were a frog, I would hide here. We scatter and start searching. About five minutes of focused searching pass when Marshall yells, "I found it!" We all hurry over to where he is standing. From between two large rocks and under forest debris, he pulls a large plastic tub. He unscrews the green cap. Inside, there are four pens, a logbook, a thank you card, a toy cartoon chicken, a small black-and-white stuffed cat and a pog, among other items. We carefully write in the logbook and put the cache back, making sure it is exactly as we found it.

It is late, and there are still no signs of alien blood or of a crashed spaceship, but we're happy about the treasure we did find. The aliens will have to wait for another night. As we leave the park, we take a moment to regroup. The woods are mysterious and I feel humbled by the greatness and possibility of them. A few minutes pass and we stand still in quiet knowing: the truth is out there. N 38° 27.120´ W 122° 40.139´

The GreatBohemian GPS Stash

HuntAt the end of this story and embedded in crunchy nuggets throughout this Arcadia issue, you'll find the curious algorithmic notations of the geocacher. That's because this treasure-hunting game is just too good not to play, so we've placed 10 of our own caches around the tri-county area coordinated to the stories in this issue, themed as it is around the idea of outer limits and hidden pleasures. Those stories whose latitude and longitude notations have "hints" appended to them hint of unsurpassed riches (OK, of miniature card decks or empty Pez dispensers), meaning that they're actual geocaches.

Intrepid (read: insane) associate editor Gabe Meline, with the gleeful help of geocache nerd and Boho intern Jackie Johansen, has organized and hidden this metaphoric gold. The rest of us just raided our closets for tchotchkes and provided empty yogurt containers to house the stuff.

As with "real" geocaches, ours provide a logbook and pen for you to note your find. We also encourage you to go online and crow about your discoveries at our Facebook page, its address being too long and ugly and messy to note here (do the usual search). If social networking is just too aught-nine for you, drop us an old-fashioned email at [email protected] or squawk of victory on the BohoBlog (www.bohemian.com/bohoblog). We trust that you'll leave the cherished objects, mostly garage sale rejects, where we placed them for the next hunter to find far into the shaded millennia—or however long used yogurt containers last in the wild.Like cleansing Dungeons and Dragons of all of its jittery Mountain Dew connotations and trotting it outside, this was pure geeky fun. We hope that you're inspired to get out and play along as you read along.

—Gretchen Giles

Send a letter to the editor about this story.