John Young never went to a drive-in as a kid but now he runs something called "guerilla drive-in," a roving outdoor movie night for people he dubs "adventure nerds."

"This is a group of people for whom a good time is maybe going out and getting rained on," said Young, 38, a Web developer from West Chester.

Exhibiting his own nerdy zeal for quests and puzzles, Young makes the audience go through an elaborate game of hide-and-seek before they get to the payoff, watching a family-friendly flick under a blanket of stars at an off-the-beaten-path spot in Chester County. The movie is pay what you want. Rain and bugs are free.

After setting a screening date, Young offers online clues to the location, which could be a train yard, a frozen riverbank, an old fort or, as on Saturday night, the top of a six-level parking garage in West Chester with a clear view of the town's clock tower for a screening of Back to the Future.

What, you wanted to just show up with a bucket of popcorn and a lawnchair? That would be way too easy for Young, a self-described geek who thinks it is more fun to find a movie than actually sit and watch it.

"He's the wizard of West Chester," said a friend, Nicole Valentine, mingling atop the crowded parking lot, as the sun set the town aglow. "He's our own P.T. Barnum."

There are other mobile movie groups, about 250 worldwide, according to the mobmov.org, but this might be the only one that sends its audience on a scavenger hunt first, said the site's founder, Bryan Kennedy.

"Each organizer brings their own personality," he said.

It's location that inspires Young, who grew up in Exton and loves digging into the community to find movie locales, such as West Chester's rail yard, where he showed The Train.

"Chester County has so many of these really amazing places. It's a nice way to take exploration to the next level," said Young.

The garage, overlooking the courthouse clock tower, was a natural for Back to the Future, where a lightning bolt strikes a clock tower, sending Marty McFly back to the future in a plutonium-powered DeLorean sports car. To enhance the mood, Young invited members of the Mid-Atlantic DeLorean Club, who showed up with six of the space-agey cars and the right waggish spirit.

"Would you like to touch my flux capacitor?" said Kevin Abato, of Landing, N.J., showing off the movie-inspired tattoo that had just been sprayed on his chest.

Young started guerrilla drive-ins in 2001 after his wife, Kate, heard about a mobile-movie group in California.

"I thought that was sooooo cool. I thought, 'Oh my gosh, I have to do this,' " he said.

The first ones were in his backyard with a few friends. He uses an old 16mm classroom projector with reels that need to be changed during the show.He mounts the projector in the sidecar of his BMW motorcycle "purely for panache," and shows it on an 8-by-11-foot curtain painted in silver and white and mounted on a plywood frame.

Since 2007, he has organized movies every six weeks in warm weather, though there was a special winter showing of The Thing, set in an Antarctic research station, next to the frozen Brandywine.

That was the time the projector blew out and a friend fixed it with a part from his car, which to Young was way more fun than the movie.

"You don't get that going down to the cineplex," he said.

Another problem arose Saturday when he realized that the garage's bright lampposts would make it hard to see the screen. So he asked for help on his Web site and Michael Lamprinos came to the rescue, devising an LED light to squash the streetlight and encasing it in a soda bottle cap.

"It not only worked, it was nerd elegant," gushed Young.

"I don't want to sound like a total geek," said Lamprinos, a low-key geologist, who was with his wife, Adrianne. "I'm really quite normal."

It was their first guerilla movie, although they tried to go to one last summer but couldn't find the "MacGuffin," the key to divining the movie's location. The term generally refers to the driving force of the movie or the thing that everyone is searching for.

"The clues were a little too easy" this year, said Lamprinos, of West Chester.

Young's MacGuffin is a waterproof case containing a transmitter wired to an old Sony Walkman that plays a continuous-loop cassette. Searchers go on www.guerilladrivein.com for hints about where the MacGuffin is (you can e-mail for more hints). Once they have a good idea of the location, they drive to the area and listen to AM 1700 on the radio, which has a quarter-mile range.

The message contains the secret access code, which they have to write down. They then take a picture of themselves at the location to prove they were there - otherwise, Young says, folks could share the code, and what fun is that? - e-mail the code and picture to Young, and he sends the location.

Last year, the MacGuffin was stashed at Jimmy John's Pipin' Hot Sandwiches on Route 202, which is full of model trains and hot dogs. This year, well, think the apotheosis of summertime.

"All I can say about it is - are you ready for the summer? Are you ready for the good times?" Young teased.

The real MacGuffin may be the actual drive-in, which for Young is just an excuse to get people together.

"I love the community. It was great to see people introducing themselves to each other, 16- and 45-year-olds, kids and parents, all found the MacGuffin and have a little tiny something invested in it," said Young, who also organizes Coworkouts, where friends bring their laptops and work outside under a tent at some bucolic location.

Guerilla drive-in fans get it. Toren Peterson met Young when he showed The Life Aquatic With Steve Zissou at a dive shop where he worked.

"He has these ideas that nobody would ever really do. But he shows up at your door and says let's do it. And you're like, what the hell?" Peterson said.

Valentine, his friend, said she goes to "any crazy plan that John can dream up. He's really into quests. You have to fulfill some terms. In this case you had to find the MacGuffin."

As the sun began to set, Young warmed up the crowd, many dressed in costumes from the movie, including a custom-made reproduction a pink, '50s-style prom dress.

"Hey everybody, are you excited to be here?" he shouted.

Then it was time to roll the first reel. As the crowd settled into their lawn chairs, technical difficulties intervened, again. There was no sound. So as usual, someone from the audience got up to fiddle with it.

Young didn't seem to mind.

"Just shout out the lines," he told everyone.

Contact staff writer Kathy Boccella at kboccella@phillynews.com or 610-313-8123.