Maryland native Jeff Krulik is a former Discovery Channel producer, and he has a long history as an independent filmmaker, with a vast oeuvre of movies exploring the weird fringes of subculture in the United States.

But the Krulik film that most people will recognize is the 1986 underground phenomenon Heavy Metal Parking Lot, a documentary about teenage tailgaters outside of a Judas Priest concert at the Capital Centre in Landover, Md. That may change soon, though, because Kulik’s latest full-length feature, Led Zeppelin Played Here, has the makings of a new cult classic.

LZPH is, at once, a documentary, a mystery, and a meditation on how the cultural institution known as the Rock Concert became ascendant. Through a combination of found footage and interviews, the movie looks to uncover the truth behind a local legend, following the cold trail of a decades-old rumor that the infamous heavy rock juggernaut Led Zeppelin played one of its earliest shows at a tiny Wheaton, Md. community center, a few miles north of Washington, D.C.

The project evolved in part from Krulik’s ties to the area, in part from his love of the subject matter—several of his previous films involve rock ‘n’ roll and its history—and in part as a sort of happy accident, by way of his interest in another Maryland-area concert of the flower-power era.

“I was always interested in the rock concert business,” Krulik says in a recent phone interview. “Where it came from; the history of it. I grew up in Maryland in the D.C. suburbs, and I looked at the things I saw there as being sort of a microcosm of what was happening around the country.

“I was originally trying to do a documentary on the Laurel Pop Festival, a festival that happened in July of 1969, one month before Woodstock at the Laurel Racetrack. Led Zeppelin was one of the scheduled acts, and in tracking the arc of that festival, I came upon this story that they played at a local gymnasium/youth center in front of only 50 people. So I found a different, better story to work with.”

But there were issues that made chronicling the truth about that alleged concert especially difficult—there were no ticket stubs to be found from that night, no cameras present to capture events, no promotional posters or critics’ reviews to offer solid proof that the show actually happened.

What he did have to work with was evidence of “an unconfirmed tour date” in Wheaton, and some documents of Zeppelin’s rambling first American tour, which took them from Denver, through a three-night stand in Detroit, to Boston and then the D.C. area. Krulik said the band apparently played a number of one-off shows in smaller venues throughout that early U.S. jaunt. “You look at their tour path—it’s evident they barely knew where they were,” he says.

“The best thing I had going cinematically was the building itself, the Wheaton Youth Center, still frozen in time,” Krulik says. “And the building spoke to me. I realized it could be a character in the film. Because it’s not just about Led Zeppelin. There were actually lots of bands who did, demonstrably, play there, like Rod Stewart and Iggy Pop. So it kind of illustrated the humble origins of the modern concert industry.”

Part of Krulik’s method was to announce, and film, a reunion gathering at the Wheaton Center for people who claimed to have been present at the Zeppelin show. The reunion ended up drawing more people than were alleged to have attended the actual performance; but Krulik says the witnesses—the more credible ones, at least—make a compelling case that the concert really happened.

“The challenge was to connect the dots,” he says. “Since there’s no hard proof, you just have people’s memories—which are based on something that happened 40 years ago. So you try to see how they cross-check. And I think for the most part, they did cross-check. But I try to let the viewer decide.”

So does Krulik believe that the Wheaton Zepplin show took place? “Oh, sure,” he says. “I believe it. But I also understand other people’s reluctance to believe it. But what convinced me was just the wealth of details that I found, talking to journalists who were covering the band, people who worked with the promoter.

“The thing is that even the smoking gun, in this case, isn’t really a smoking gun. You can still poke holes in the best evidence, if you’re so inclined. Finding the smoking gun has been elusive for 40 years. But I managed to find a lot of the key players. I’ll pat myself on the back for that, although I had a lot of help.”

Led Zeppelin screens on Friday, June 13 at 9 p.m. at Scruffy City Hall as part of the Knoxville Film and Music Festival.