Tickled boasts a premise so irresistible you can’t imagine how the documentary will actually measure up: It’s about a reporter who stumbles across something called the Endurance Tickling Competition. And no, this is not a Christopher Guest mockumentary. When the reporter investigates, he discovers something far more twisted and nefarious than anyone could imagine. It sounds like the kind of movie you might select on Netflix in a late-night daze, and in a larger sense, that’s the right time and place to view it. Tickled starts out as a quirky comedy but builds into something dark, menacing, and even profound.

Our amiable guide is David Farrier, a pop culture reporter from New Zealand who gets sent a few YouTube videos of strapping young men tickling each other (while the tickle recipient is tied down). As soon as he makes a few inquiries, he begins receiving threatening and derogatory notes from a mysterious woman who runs the competition. She warns him against pursuing his story, and throws in a few homophobic slurs while she’s at it. The threats only further pique Farrier’s interest. Casting his own career and concerns for his personal welfare aside, the intrepid journalist begins a journey that takes him to Los Angeles, Long Island, rural Michigan, and some even darker corners of the human soul.

Such a bizarre story requires a firm directorial hand, and in their debut film, Farrier and his partner Dylan Reeve prove to be remarkable masters of tone. The first third moves along with a winning briskness, relying mostly on the novelty of the idea and Farrier’s deadpan kiwi humor to draw you in. As they meet and interview others whom the mysterious woman has threatened they slow down, let the novelty fade away and the reality sink in: This is a tickling competition that has the power to ruin lives. In one extreme case, the menacing woman at the center of their investigation even email-bombs the White House on behalf of a disgruntled former employee, prompting a visit from the Secret Service to the poor kid’s dorm room.

So what is the purpose of all this tickling? It doesn’t take a genius to figure it out. When one of the participants admits (while being tickled), “I’m being violated in so many ways right now,” and another says, “I’m not naked, but I might as well be,” the subtext rises quickly to the top. Farrier discovers that tickling is a bona fide fetish, and he finds other tickle video producers who seem more at peace with their work.

It’s a deeply involving story that spins out rays of meaning: social, economic, and psychological. But what we’re ultimately left with is the laughter. The giggles you hear in Tickled are infectious, and in all the worst ways. It’s hard not to smile when you see someone being tickled, but what if that person is tied down and it appears to be against their will? What if you know this video will be used to humiliate and intimidate them later? What if it means they can’t get a job, or they will go to jail? And what if you still laugh? Farrier and Reeve leave that question unanswered, but the value of their work is clear: This documentary is either the scariest comedy or the funniest horror movie ever made.

Tickled opens Friday at Atlantic Plumbing Cinema.