Search party

Heeding the commands of ghostly voices, David Bitkower and his friends race through the darkness to Paul Revere's famous statue. Like amateur sleuths, they huddle together under a lone flashlight, punching buttons on Bitkower's cellphone until a clue appears on the glowing screen.

`` I'm not sure why the ghosts are asking this," says Bitkower, a benefits adjustor from the South End, reading his screen aloud, `` but they want you to count all the trees on Paul Revere Mall. You have two minutes."

The team scatters frantically. ``Did you count the trees on this side?" ``I got 43!" ``Whatever it is, just enter it!" Finally Bitkower types in the answer and the group bolts onward, another problem solved on the new Ghosts of Liberty mystery tour, running through Nov. 1 in the North End.

Bostonians got their first taste of interactive adventure gaming two years ago with the premiere of Tomb, a contest in which participants don archeologist hats and traipse through a re-created Egyptian crypt trying to solve a pharaoh's riddle. Now comes Ghosts of Liberty, in which players are cast as secret agents and are set loose on Boston's streets, following clues on pre-programmed cellphones and cues from disguised actors wandering about as they hunt down a creepy terrorist.

High-tech scavenger hunts in public spaces have been popular for several years, with a San Francisco-based company, The Go Game, at the forefront of the genre. But the creator of Ghosts, Nicholas Tommarello, is trying to add a new wrinkle: reality-based mobile phone games that appeal to tourists as well as locals.

By visiting landmarks such as the Old North Church, reading historic markers on Cross Street, and reciting Longfellow poems, Ghosts players absorb city history while figuring out the mystery. Next spring's game will have tourists sleuthing through Harvard Square.

``I can't stand being on a tour bus," explained Tommarello, 27, who started his company, Urban Interactive, three years ago while in Babson College's MBA program. ``You basically have to listen to this guy drone on over and over and over again. They make you go at their pace. . . . I wanted something that's structured, yet you're independent enough to do what you want -- something that's structured but still lets you have fun in a unique way."

Urban Interactive ran its first ``augmented reality" game in the fall of 2004 as a corporate team-building exercise. Cellphone-wielding participants were sent scurrying through the Museum of Science in search of clues and props as they tried to construct a faux fusion reactor.

``We were looking at the traditional group hugs and trust falls for team building, but that really wasn't what we were looking for," said participant John Kendzior , manager of employment services for Harvard University. ``This game really weaves in a lot of unique elements. It's fast-paced and thought-provoking. It's collegial -- it allows you to work closely with others in problem solving. It's kind of a blend between `The Amazing Race' and the TV show `Treasure Hunter.' "

The inaugural Ghosts game was held last Friday, the 13th. Six teams, including a birthday party of teenagers from Wellesley, gathered at Paddy O's pub on Union Street at 6:30 p.m. They had paid $60 per team to play.

Met by a ``secret agent," Bitkower's foursome was handed a cellphone programmed with all the night's clues, an ultraviolet pen, a map of the North End, a ``classified" case briefing, and a folder to open in the event of an emergency (i.e., if they became hopelessly lost).

Tumbling out of the bar, the group hardly appeared to take the mission seriously. ``Are we really doing this?" said teammate Jim Wolfe, an electronic design engineer who lives in the South End. But when another group almost passed them at the first challenge, they began playing for keeps.

Wolfe's wife, Nan, a kitchen designer, took over as master code-breaker, jotting down letters and numbers from bronze plaques and muttering aloud solutions. Bitkower, the group's text-message fanatic, was glued to the cellphone, tripping over cobblestones and even a small fence in his haste to relay information from digital maps, text messages from ``Director Finch," and voice mails from a ghost-channeling psychic to the group.

As the team raced down Salem Street past Bova's Bakery , Jim Wolfe signaled to turn left instead of right -- to throw other groups off their scent. ``I feel like we're behind," said Jerry Ringuette, an information technology specialist from Quincy, before sprinting down Commercial Street in search of a woman's feather boa.

Lost on Hanover Street, Bitkower slyly reached into his coat pocket for a travel map. ``We brought a cheat sheet," he whispered.

``We're running through a city like a bunch of maniacs," said Ringuette. ``Everyone seems to look at us almost like we have five heads, but we don't care."

Two hours, 10 riddles, and several spooky alleyways later, the group reached the finish, with Tommarello standing there to congratulate Bitkower's crew, which ended up winning. If their score remains unbeaten during the game's two-week run, they'll win a prize of either an Xbox 360, a $300 iTunes gift card, or dinner for four at Strega. (The score takes into account a team's time as well as certain bonus points and deductions.)

"In college many, many years ago we did a game of 'Gotcha!' based on the movie where we chased [each other] with fake guns," said Bitkower. "I haven't had this type of fun in a while."

"This is more of the North End than I saw in the six years I lived here," said Jim Wolfe.

Tommarello wants to take Urban Interactive online, offering copies of the game's software to the public so that anyone in the country can create their own wireless adventure based on their hometown's tourist sites.

If successful, tourists would be able to download games onto their phones for virtually any vacation destination.

For now, though, Tommarello just hopes that people believe in Ghosts.

"I use lots of analogies: It's part interactive theater, part scavenger hunt, part treasure hunt, part choose-your-own adventure novel," he said. "You've got to play it to understand. It's different."

Ghosts of Liberty tours depart from Paddy O’s, 33 Union St., between 6 and 7 p.m. nightly. The cost is $59.95 for a team of up to four players. Reservations are required. For more information call 800-930-7517 or visit ghostsofliberty.net.