Mar 27, 2012 10:26 AM

For locals, the corner of County Road 39 and North Sea Road in Southampton isn’t complete without Tom Wedell—a lone man waving, smiling and toting his “Deport Illegals” sign across the street from an army of immigrant workers, legal and undocumented alike.

Driving by this familiar scene on a daily basis, documentary filmmaker Dennis Michael Lynch never gave it a second thought. But that changed on an autumn day 16 months ago when he was stuck at the corner’s red light with the top off his turquoise Jeep Wrangler, listening to people honk their horns in encouragement at Mr. Wedell or scream out nasty comments from their rolled-down windows.

Then, Neil Diamond’s “America” happened to come on the radio.

“It all just started to connect,” Mr. Lynch, a self-declared “big Neil Diamond fan,” recalled during a telephone interview last week. “Tom Wedell. The 100 guys standing on the opposite corner from him. I thought, ‘I have to see what this guy’s deal is.’ I pull over, and I had my camera guy with me there at the time, and I started BS-ing with Tom. I told the camera guy, ‘Get that thing, turn it on.’”

And so began Mr. Lynch’s most recent documentary, “They Come To America,” which is debuting in an exclusive, one-night screening on Saturday, March 31, at Guild Hall in East Hampton—the same venue for his first movie’s debut, “King of the Hamptons.”

“They Come To America” whittles down more than 100 hours of footage into 100 minutes and focuses on the human and financial costs of illegal immigration, Mr. Lynch said. He added that he’s never seen another film tackle the issue from both sides of the political spectrum.

Over 14 months, Mr. Lynch shot footage with a four-man crew in Arizona, California, Illinois, Florida, Washington, D.C., Colorado and New York. A third of the film takes place in the Hamptons—around both Southampton and East Hampton towns. That action happens inside the home of an illegal family here and even in the filmmaker’s own backyard in East Hampton.

Across the country, the crew covered debates, rallies, events and traveled down to the Mexican border, where they were chased by the drug cartel, Mr. Lynch said. In contrast, politicians ran away from the cameras when pressed with the tough questions, he said.

“My hope was to create a film that Congress would not be able to ignore,” Mr. Lynch said, noting that he independently funded the project. “This is the film that so many people don’t want you to see. This is the sort of film that can spark change.”

From the movie’s beginnings on that street corner in Southampton, Mr. Lynch instantly realized the gravity of one of the hottest political topics in the country: illegal immigration. In just a half hour, the 42-year-old, non-political filmmaker heard some passers-by praise Mr. Wedell as the biggest patriot in America while others called him a racist behind an American flag, he reported.

“Never once, I swear to you on my life, with the things that people say to him and throw at him, did he ever, ever use a curse word,” Mr. Lynch said. “I had people stand in front of him, throw shit at him, say, ‘You f---ing [expletive]. You are an embarrassment to America.’ You know what he’d say? ‘Thank you for sharing your opinion.’ If someone did that to me and threw a cup of coffee on me, the situation wouldn’t have been like that. That guy’s been stabbed, shot and gets death threats all the time.”

Leaving the scene, Mr. Lynch knew illegal immigration had to be the topic of his next project, even though before that day he’d never given a single thought about it. And so, he rounded up and filmed those who had—ranchers, lobbyists, school and hospital administrators, immigration experts, and even the undocumented immigrants holed up in the Hamptons.

“If I was going to make this film, I needed to know what the hell I was talking about,” Mr. Lynch said. “So I found the people who did on both sides of the issue. That was the style I took: go down the middle of this topic and just let the camera tell the story.”

The camera does just that during the crew’s three-day campout on the United States-Mexico border in Arizona.

“We were in the dirt,” Mr. Lynch recalled. “We put ourselves in harm’s way up against the drug cartel. We were warned by police, ‘Do not go down there. We do not go down there.’ We went down there. You cannot describe what is going on with illegal immigration, especially at the border, unless you see it and live it.”