First, a story.

Back in 1992, I went to a 20^th anniversary midnight screening of director John Waters’ infamous cult film “Pink Flamingos” at Portland’s late, deeply lamented Movies on Exchange Street. In the scattered but eager audience was a young couple, presumably thinking a date night at one of the most inescapably outrageous and offensive movies of all time was a good idea. Barely into the film (and certainly long before “that scene” that Waters aficionados have burned into our brains), the couple fled the theater, something that, while understandable at any John Waters screening, was perplexing at a celebratory midnight showing. (Although no doubt Waters would have been pleased.) After all, some movies practically dare you to walk out.

And that’s where “Thundercrack!” comes in. Screening at the Apohadion Theater on Monday, July 22, this 1975 horror comedy may not be as well-known as Waters’ legendarily outrageous films like “Pink Flamingos,” “Polyester” (with its scratch-and-sniff cards) or “Desperate Living,” but it’s not for lack of trying. Cited as an influence on the shock cinema of Waters and others, “Thundercrack!” emerged from the fecund imaginations of experimental filmmakers Curt McDowell and George Kuchar, who teamed up to bring forth a truly bonkers hybrid of horror, Hollywood melodrama, comedy and, well, pornography. (Like “Pink Flamingos,” “Thundercrack!” incorporates unsimulated sex – of various types – into its deliberately transgressive mix.) Like Waters’ work, Kuchar and McDowell’s movie – shot on a shoestring on scratchy black-and-white 35mm – is a genre-defying, button-pushing, borderline unpalatable act of cinematic aggression against any brave suckers willing to subject themselves to its grubby charms.

“ ‘Cult film’ gets thrown around a lot as a term – with, like, Cinemagic showing ‘Crouching Tiger, Hidden Dragon’ and calling it a cult film or something – but this is the real deal.” That’s the Apohadion’s Greg Jamie, who’s turned the Bayside venue into a much-welcome hotspot for Portland moviegoers looking for cinematic adventure. Says Jamie proudly, “We like imagining Apohadion as a sort of cult art-house cinema one night, a noise show spot the next night, a folk venue the next night.  Showing a two-and-a-half-hour, black-and-white, mid-’70s oddball horror-comedy-underground-porno written by and starring a legend in experimental film just seemed like the best way to say how we’re feeling in Portland in the middle of tourist season.”

Gauntlet thrown.

“Thundercrack!” follows the template of the creaky “old dark house” horror classic, with a creepy (and obviously fake) mansion, a stormy night, a creepy mistress of the manor (wild-eyed Marion Eaton, channeling Joan Crawford at her most indescribably bananas), several carloads of unsuspecting travelers seeking shelter, deep dark secrets and lots of random encounters by candlelight. Toss in an amorous gorilla and hardcore scenes (where the actors continue to spout screenwriter Kuchar’s absurdly purple dialogue throughout), and some serious gross-out elements just for the heck of it, and that’s almost enough to encompass the scabrous 1970s lunacy that is “Thundercrack!”

So why would anyone go see such a film (even if it’s screening not at midnight but the more reasonable hour of 7:30 p.m.)? Well, for one thing, there are those of us who seek out the fringes, knowing that that’s the only place where underground, experimental, subversive or otherwise marginalized filmmakers are left alone to bring their stories to glorious, often shocking life. For another, as Jamie says, George Kuchar (who appears in the film as the gorilla-loving weirdo, Bing) is no joke, his boundary-busting films held in high regard in critical and historical circles. At least by those brave enough to seek out Kuchar classics with titles like “Hold Me While I’m Naked,” which was listed at No. 52 in a 2000 Village Voice critics’ poll of the 100 best films of the 20^th century.

“This one fits in with what we’re trying to do at Apohadion for film, I think,” says Jamie. “I got into George Kuchar in college when I took an experimental film class. Since then, I occasionally got to see Kuchar films at Anthology Film Archives when I lived in New York, but I hadn’t heard of ‘Thundercrack’ ’til kind of recently.” And while – due to time constraints or timidity – Jamie admits he hasn’t had a chance to screen “Thundercrack!” for himself just yet, he’s still thrilled to inflict its entire, 159-minute running time on the rest of us.

“Look,” confides Jamie, “I’m screening this one sight unseen. I got a copy of it (the unedited 40^th anniversary Synapse release) and I feel like the right thing to do is share it with as big a group as possible. It’s gonna be offensive.” Agreeing that the screening is part of the Apohadion’s efforts to “keep Portland weird,” Jamie says, “Maybe it’s too late, but let’s try to tip the scales when we can.”

So that’s a warning – and, you know, an enticement. At least for those of us who delight in turning over cinematic rocks to see what lives down there.

“Thundercrack!” will screen on Monday, July 22 at 7:30 p.m. at The Apohadion Theater (www.theapohadiontheater.com). Tickets are $8, and you have to be at least 18 to get in. Seriously.

Dennis Perkins is a freelance writer who lives in Auburn with his wife and cat.