When Shane Carruth’s Upstream Color premiered at the Sundance Film Festival in 2013, one of the only available promotional images for the film was a pitcher of ice water. The pitcher sat on a table with book whose title we cannot see, close to pair of legs whose owner we also cannot see.

The image was the opposite of promo enticements we’re used to absorbing (a good-looking movie star, an evocative landscape or piece of architecture, anything else really) because marketing experts likely cling to the conventional wisdom that pitchers of ice water are not a great hook. This was the rare case where your dad’s quip about Picasso, “I could make that at home,” was actually true.

It should come as no surprise that Carruth — who wrote, directed, produced, co-edited, and composed Upstream Color, and cast himself in one of the leading roles — also distributed the film himself, so he could control the way it was presented to an audience. As he put it in an A.V. Club interview with Sam Adams:

… it begs the question, ‘Why am I looking at a water pitcher?’ ‘Whose is this elbow and these legs that are offscreen, or almost offscreen?’ And that’s storytelling as well. It’s like asking a question and if it’s a compelling enough question, maybe the audience will care enough to want to know the answer.

If you’ve seen Upstream Color, you know some of these answers. The water is imbued with tremendous significance because Kris (Amy Seimetz), a woman kidnapped and held under hypnotic suggestion, is told that it’s special, better than anything she’s ever tasted. The book on the table is Walden, by Henry David Thoreau, whose ideas about living simply and returning back to nature are deeply embedded in the film. In fact, this mundane-seeming shot is as thematically loaded an image as any Carruth conjures, but that can’t be understood by anyone who hasn’t processed it yet.

Carruth chose to self-distribute Upstream Color because he wanted to create the right “context” for viewers to experience it; “What the hell am I looking at?” is a fine place to start.

In the five years since Carruth released Upstream Color, audiences have become accustomed to the world-building and large-scale serialization of the Marvel Cinematic Universe and Game of Thrones, and the dense puzzle-box intrigue of shows like Westworld and Counterpart, but Carruth’s film continues to linger because it cannot be solved. Upstream Color exists just outside the realm of comprehension, which isn’t a bug but a feature, designed to keep the mind circling back to it like some unscratchable itch that flares up every once in a while. Some filmmakers like to give viewers something to solve—Westworld co-creator Jonathan Nolan has deliberately teased the Reddit crowd with little mysteries and Easter eggs, often to the show’s detriment— but it takes an audacity to leave a few ellipses and risk riling up the sleuths.

For Carruth, Upstream Color was the next logical step after his debut feature Primer, which had won top prize at Sundance nine years before. If Primer itself wasn’t so good, it would have been overwhelmed by the unlikeliness of Carruth’s story. Shot for just $7,000 — on 16mm, no less — the film is perhaps the most significant piece of outsider art since Herk Harvey, an industrial filmmaker from Lawrence, Kansas, gathered the resources to make the eerie, 1962 cult fantasia, Carnival of Souls. A former engineer and mathematician from Dallas, Texas, Carruth is an autodidact whose work suggests the beginnings of a Silicon Valley legend, someone who saw the future from his garage. That’s the basic premise of Primer: Two guys accidentally create a time machine from a suburban garage and set themselves — and likely humanity itself — on a catastrophic course.

The timeline in Primer is solvable, though not after first (or second or third) viewing, and probably not by the fragile-brained among us. Seven years after its debut, a chart was created that mapped out the doubles and timeline overlaps that metastasize as these inventors — and their doppelgängers — continue to activate the continuum-bending machine they’ve tucked away in self-storage facility. Fully processing the chart would take another seven years.

Though spackled with wit (“Are you hungry? I haven’t eaten since later this afternoon” is a favorite), Primer doesn’t dumb down the technical language of its engineers or make itself immediately graspable, which is a luxury an auteur can afford at the low, low price of $7,000, when no one is looking over his shoulder. The end of the film suggests infinity, if not the apocalypse: Mess with time too often and the possibilities are endless, provided the universe doesn’t implode.

By the time he finally made Upstream Color, Carruth’s reputation as a brilliant recluse had ballooned to Kubrickian proportions, bolstered by Primer’s cult status and buzz over A Topiary, a globetrotting project so ambitious that its failure to get made somehow burnished his image. (Ditto The Modern Ocean, which was announced after Upstream Color in 2014 and still hasn’t been produced, despite a testimonial from Tom Holland that it’s the greatest script he’s ever read.)

Though still working DIY-style on a minuscule budget, Carruth had the resources to take a great leap forward in terms of cinematic brio, because he didn’t have to simply stage scenes and rely on what’s on the page. That’s not to say Primer isn’t visually compelling — on the contrary, one of its miracles is creating sci-fi ambience from spit-and-glue production values — but on seven times the budget, he could transcend the page completely.

There are plenty of memorably strange lines in Upstream Color (“I have to apologize. I was born with a disfigurement where my head is made with the same material as the sun.”), but vanishingly little dialogue. Characters speak but rarely to each other, which is Carruth’s way of emphasizing both the distance between them and otherworldly connections that cannot be made through speech. Much like the later work of another reclusive Texan, Terrence Malick, the film is intended as an intuitive, emotional experience, rather than an abstract game of connect-the-dots. How you feel watching Upstream Color is more important, to his mind, than how much you understand what’s going on.

Here’s what we do know: There’s a type of larva harvested from an exotic plant that, when ingested, has a hypnotic effect on the human mind. As the film opens, an unnamed nefarious character, referred to in the credits as the Thief (Thiago Martins), taser and abducts our heroine, Kris (Amy Seimetz), at a club and forces her to swallow a larvae. In her suggestible state, the Thief then instructs Kris to hand over her collection of rare coins and drain thousands from her home equity and bank account. She awakens to the worm still moving through her body and attempts a particularly gruesome act of Cronenbergian surgery to get it out, but the task falls to another mystery man, called the Sampler (Andrew Sensenig), who transfers it to the body of a pig. As one does.

A year later, she and Carruth’s character, a disgraced broker named Jeff, meet in a serendipitous moment on the train. But it soon becomes clear that they’ve suffered similar trauma, even though they have no memory of what happened to them. Their relationship, premised on a suffering neither of them can identify, fuels a mutual paranoia that draws them to each other, even as it separates them from the world.

Much of what happens next is harder to understand — like, say, a sequence where the Sampler tosses a sack of piglets into a river, a blue substance transfers from their bodies to the roots of a tree, and the orchids start to grow, ready to be harvested again. Or, more peculiar, a phenomenon where Kris and Jeff’s personal histories start to merge, and Jeff passes off Kris’ childhood stories as his own. And what does the Sampler want, anyway? Is he a hero, a villain or none of the above?

Upstream Color sends you scrambling for clues. What’s the meaning of those implanted Walden quotes that Kris robotically recites from memory? What’s the purpose of the foley work the Sampler samples and releases through the Quinoa Valley Recording Company? How does Kris’ false pregnancy relate to her pig’s real one?

There’s plenty of room for speculation over any and all of these questions, but unlike the mappable timeline chicanery of Primer, they’re unmoored and abstract. Carruth has full command of his effects in Upstream Color, but he doesn’t seem interested in directing viewers toward specific conclusions more than general ones.

The film is perhaps best seen as a grown-up, experimental riff on Close Encounters of the Third Kind or E.T.: The Extra Terrestrial, playing on the same extrasensory connections between different beings. Much like Richard Dreyfuss and Melinda Dillon in Close Encounters, Kris and Jeff have had an alien experience that bonds them closely, but that no one around them can understand. Absent any tangible evidence, they go off searching blindly for answers, following the strange whims of their intuition like breadcrumbs through a forest. There’s little difference between Dreyfuss carving Devils Tower out of a pile of mashed potatoes and Jeff digging up the backyard to locate what Thoreau would describe as “a low and distant sound.” Both scenes teeter between wild paranoia and unshakable, unaccountable conviction.

The connections, too, between the characters, like the merging of Kris and Jeff’s histories or the odd syncopation between their lives and those of their porky counterparts, recall the merging consciousnesses of Elliott and the alien in E.T.. At a certain point, Kris and Jeff are not merely united by circumstance, but intertwined in ways that they (and the film) cannot explain. Robbed of their individual identities by the Thief, they evolve into compatible and co-functioning organisms, which in Carruth’s world counts as an honest-to-goodness love story. They experience a kind of death after their lives are stolen, and the film brings them around to a form of renewal.

That’s where Thoreau steps in again. Once a tool of distraction for the Thief, Walden becomes the blueprint for Kris and Jeff’s future — and for Carruth’s Malickian embrace of the natural world. Upstream Color ends in a place where all those who have been stripped of their money, jobs, and personhood arrive like Thoreau in the first lines of the book, living and laboring in the open air in their version of Walden Pond, which here happens to include orphaned livestock.

The interiors that Carruth shoots in antiseptic white — the sleek office where Kris works in graphic design, the pristine hotels that are both living and work space for Jeff — suddenly open up into the exalted beauty of this rural idyll. It isn’t clear where anything goes from here, but it feels like a triumph, like some hard-won emergence from the pupal stage.

Where Carruth goes from here is another mystery; it’ll probably take another few years to resolve. But Upstream Color feels like an evolutionary jump in a career that’s still in its infancy, and still, due to Carruth’s DIY iconoclasm, happening far outside the Hollywood incubator. For now, the best he can do is leave us guessing.