The treasure hunters move slowly forward, eyes fixed on the screen of a handheld GPS unit, which shows an arrow and a steadily decreasing distance-to-destination.

She watches the screen, while he checks around for people who might be watching them. No need to tip someone off to the location of the cache. That would be against the rules of the game.

Soon, they have found the general location of the hidden treasure, and it’s just a matter of figuring out exactly where within a 20-foot radius or so that it’s been hidden. Often, though, that turns out to be the hard part.

Pam and Tom Dubois are geocaching, and they’re hot on the trail of a new find.

For the uninitiated — people whom geocachers like Pam and Tom would call “muggles” — geocaching (pronounced geo-cashing) is a sort of modern-day hide-and-seek game for hidden treasure. Emphasis is on the word “hidden,” not “treasure,” as caches normally contain trinkets, small toys, coupons and other items of questionable value.

The caches — which are waterproof containers that range from the size of a pencil eraser to ammo boxes and even larger — are hidden by participants who upload coordinates and clues to the Internet. They are found by other “cachers,” who download that information and then head out into the field with a GPS receiver and a pen to sign the logbooks once they find the caches. Usually, the finder is encouraged to leave something in the cache if he takes something out.

Clearly, it’s not your old-fashioned treasure hunt.

“I use multi-million-dollar satellites to find other people’s junk.”

That’s the message on one of downtown Suffolk resident Tom Dubois’ favorite bumper stickers, and it irreverently sums up the hobby of geocaching. But there’s much more to the pastime than looking for junk, as evidenced by the fact that he and his wife have logged more than 635 finds since they started caching last summer.

“The main thing about geocaching is that it will take you places in your hometown that you never knew existed,” he said.

Like the cable-driven ferry five miles down a dirt road near Murfreesboro, N.C. Or the church in downtown Suffolk with a Civil War-inspired stained-glass window. Or the church where they met a fellow cacher, an Episcopal priest who had hidden caches at each of the Episcopal churches in the area.

There are 20 different caches located in the downtown area of Suffolk, alone. Within a 30-mile radius, that number jumps to more than 1,300, and it’s growing every day, as more caches are hidden all the time.

In March of this year, the number of active caches worldwide surpassed the million mark, according to Groundspeak.com, the organization that was formed in 2000 to support the growing community of geocachers. Groundspeak claims a community of more than 3 million treasure hunters in more than 150 countries.

There are geocaches in Iraq and Afghanistan. There are caches hidden underwater — accessible only to those with SCUBA equipment — and on rock faces — accessible only to those with climbing gear. There is even a cache aboard the International Space Station, left there by astronaut/geocacher Richard Garriott. Pam and Tom Dubois joke that they’ve set a goal to find and log that particular cache one day.

Most caches, however, are far more accessible, if not precisely easy to find.

“BeanerPops Goes to Oderzo,” for example, is located in a small park-like area beside the Godwin Courts Building. “Keep Looking” is near a municipal parking lot on S. Saratoga Street. “Lynette’s Lair,” whose name plays on the fact that Suffolk Tourism Development Manager Lynette White works nearby, can be found near the Prentis House, where the city’s Visitor Center is currently located.

The names are set by those who hide the caches — the cache owners, in the parlance of geocaching. Sometimes the names, themselves, are clues to their locations, sometimes they’re whimsical comments on the community, and sometimes they’re simple identifiers.

After taking some time to learn about the hobby by spending weekends and even a short vacation searching for caches that others had hidden, Pam and Tom Dubois — known as Suffolk Nana & Papa in the geocaching community — decided to hide a few treasures of their own.

With Tom’s background in management on the nuclear side of the shipyard, it was, perhaps, not surprising that the couple settled on a series of somewhat sterile names for their 14 caches hidden around the city. “Suffolk History 001” takes cachers behind a well-known downtown business and gives them a look at a part of the city’s past that they might never have known about. Thirteen “EGGS” — Easy Guardrail Grab Series — caches give searchers a tour of some of the city’s best-known features.

When someone finds one of Tom’s caches and logs the find online, Tom receives a message, so he can keep track of how popular the cache is in the community. A “did not find” message lets him know that the cacher was unable to locate the treasure. A string of DNFs alerts Tom that something may have happened to the cache.

It happens. Sometimes, a landscaper will find and remove a cache. Sometimes a muggle will see cachers fiddling with the cache and discover it on his own.

Muggles, which take their name from non-magical people in the popular Harry Potter book series, are people who don’t know about geocaching. One of the unofficial rules for the loosely organized geocaching community is to keep the muggles clueless about a search.

“If there’s people around where we think a cache is,” Pam Dubois said, “we’ll just move on.”

The whole concept of muggles betrays an interesting characteristic of the geocaching culture. It is a community with, shall we say, more than its share of self-proclaimed geeks. (“I’m not a super-geek,” Tom said, “but I’m a geek.”)

Such a community would be expected to develop a broad new language for its activities, and geocachers do not disappoint in this regard. Sprinkled in amidst a head-spinning number of acronyms (GPS, DNF, TNLN and others, for a start), there is talk of attributes, benchmarks, geocoins, hitchhikers, reverse caches and Travel Bugs — all of which should help keep the average muggle pleasantly clueless.

But those who hear about the hobby and think it might be interesting will find that there are few pastimes that are easier to get involved in. A GPS receiver and an Internet connection is all that’s necessary. Knowing a geocacher can help, though.

The online community, which can be found at www.geocaching.com, includes forums that allow geocachers to contact one another and organize special events together. As with many hobbies, those who are involved in it often bring others into the action.

Pam and Tom Dubois were introduced to geocaching through their daughter and son-in-law, as well as one of Tom’s co-workers. Pam found their first caches — “Hair Today” and “Suffolk is Art-Full” — on successive days last June, and they’ve been hooked ever since, ready and eager to teach newcomers the art of the search.

They recently completed a drive around the four-state region, a mini-vacation that was devoted entirely to finding caches. It was a fun trip, both said. But Pam learned a lesson that is a common refrain for geocachers.

Don’t forget to look up from the GPS receiver and see the scenery. After all, the whole point of most caches is to show the treasure hunters something new and unusual about a location they may have seen so many times before that it had begun to fade into the background.

“On that four-state trip, I missed all of what we passed” because of watching the GPS, she said. It’s not a mistake she plans to make again.