“Capturing Bigfoot” doesn’t waste time getting to the hairy meat of the matter. It opens with the shaky, grainy 16mm footage that’s the most widely viewed piece of cinéma vérité in history apart from the Zapruder film. It even looks like the Zapruder film — though the setting, in this case, is a woods, full of birch trees and sunlight and vivid autumn color. For a few moments, the image jerks around in a raw amateur way. Then it grows steadier, and there, about 100 feet away from the camera, an ape-like figure walks along in front of the forest foliage, turning its head for an instant to look at the cameraman, then continuing on its way.

This famous evidence of the creature known as Bigfoot was shot by a man named Roger Patterson in Northern California on Oct. 20, 1967. The footage lasts just 59 seconds. We don’t get to spend much time gawking at the creature (it’s only a tantalizing glimpse), but he’s there just long enough for us to notice several things. The hair on his back looks a bit shiny. And is it our imagination, or is this primitive creature not just walking but strolling, with a rather jaunty sense of purpose?

Why did this footage possess the world? As an opening title informs us, “No one has ever been able to determine whether the film is real or a hoax.” Then it adds, “Until now.” “Capturing Bigfoot” is an astounding documentary about the legend of Bigfoot — about how it was born, how it took hold, and how that iconic piece of film footage came to be. It’s a documentary that answers all the questions and solves all the mysteries. Unlike your typical film about UFOs, it doesn’t leave you with that vague feeling of “The truth is still out there, and I’m still not sure what it is.” “Capturing Bigfoot” shows you the truth, but what it really shows you is what that truth says about us, a society that went down the rabbit hole of wanting to believe and now, increasingly, lives there.

“Capturing Bigfoot” is being released at the perfect moment, when belief in the uncanny has been given a new “credibility” by the testimony of select U.S. military officials about the reality of UAPs — but, at the same time, certain legendary mythologies about an existence beyond ours have now been unmasked as hoaxes. For decades, the 1934 photograph of the Loch Ness Monster was a haunting image of a lost world. In 1994, it was revealed that two men had created that image out of woody putty attached to a toy submarine. And in 1991, Doug Bower and Dave Chorley explained that they created the crop-circle phenomenon by going into a field and making one, in 1978, after an evening spent at a pub. As someone who’d spent many hours gawking in wonder at photographs of crop circles, I greeted the revelation of that hoax with a crestfallen fascination. I no longer flirted with the teasing possibility that crop circles could have been created by a force from another world. Somehow, though, the melting down of that possibility made our own world seem smaller.

But the Bigfoot legend never loomed in that way, at least not for me, because there was always something fishy about it. Starting with this: If there was a “Bigfoot” living in the woods of Northern California in the late 1960s, wouldn’t it have been seen by someone other than Roger Patterson and his camera? Marq Evans, the director of “Capturing Bigfoot,” digs into the Bigfoot legend with an investigator’s wide-eyed curiosity and cunning. For a while, he zeroes in on Patterson, the Zapruder of the saga, who died in 1972. The film goes back to paint a portrait of this eccentric resident of Yakima, Wash., who became obsessed with the idea of oversize simian humanoids going back to the late ’50s.

Patterson, with his light drawl and camera-ready affability, might have stepped out of the ancient version of an Errol Morris film, back when Morris was the snarkster of “Gates of Heaven.” His obsession was touched off by an article in True magazine in 1959 (we see the article; it was entitled “America’s Abominable Snowman”). And, of course, the legend that Bigfoot emerged from had actually been around for centuries, going back to the Himalayan myth of the Yeti (in British Columbia, it became the Sasquatch).

Patterson would take his young son on camping trips in a VW van up into the mountains of Northern California, on the lookout for Bigfoot. He would stuff two live horses into the van — an indication, right there, that he had a bit of a screw loose. But he was cosplaying at being a cowboy. He was a rodeo rider, and with his rifle and cowboy hat and drawling aw-shucks attitude, he made himself into a camera-ready character. His ingenuity was tapping into what we might at the time have called National Enquirer culture: its tall tales and legion of readers. This was the true silent majority of the New America. We see old footage of interviews with people who claim to have had Bigfoot sightings, which are just like the interviews with people who claim to have had alien encounters.

Patterson’s son, Clint, now in his late 60s, is the documentary’s central figure. He resembled Bill Paxton, and he’s like a Bill Paxton character. “When I came out of my mom’s vagina,” says Clint, “they put a cowboy hat on me.” He means that literally. (It tells you what you need to know about this family.) Clint, for most of “Capturing Bigfoot,” remains a true believer in his dad’s 59-second Bigfoot film. And there are expert witnesses who testify as to why it has to be authentic. One is Dr. Jeff Meldrum, a professor of anatomy at Idaho State University, where he’s got an “Evolutionary Morphology Laboratory” that’s essentially a Bigfoot room, with models, evidence, and an example of the 16mm camera Roger Patterson used. Meldrum says that watching the footage, he can identify detailed muscle groups in Bigfoot, and that the creature is clearly real. (One interesting detail: The Bigfoot we see in the footage is female. She has mammary glands.) And Bill Munns, who worked as a make-up artist at Universal Studios starting in 1969, explains that the image of Bigfoot in the footage could not have been a man in a costume. Even Hollywood, he says, did not have the technology at the time to make an ape-man look that good.

But then the movie starts to piece together the story of how that footage came into existence. Roger Patterson was, among other things, a canny visual artist who, in 1966, wrote and published a book about Bigfoot entitled “Do Abominable Snowmen of America Really Exist.” It was illustrated with his lavish drawings. And Clint Patterson talks about how as a boy, he once went into his father’s shed, which was usually locked, and found a pile of second-hand fur coats.

Using his 59-second film, Roger Patterson was able to turn Bigfoot into a phenomenon. He went on the talk-show circuit (Johnny Carson, Merv Griffin, Art Linklater), making himself into a found-object celebrity. The Bigfoot footage, as Clint puts it, “went viral before the word viral even existed.” It was given credibility by being featured in scientific magazines, as if it were an anthropological discovery. And the film, in its Zapruder-like “authenticity,” was seen, in its very semiotics, as a document of something real. Patterson played it in movie theaters, on a road-show tour, charging $2 a ticket, then moving on to the next town. In the Salt Palace in Salt Lake City, one of his associates recalls that “We played two weeks after Simon and Garfunkel, and took more money out of the building than they did.”

The money, which added up to many millions in today’s dollars, was a blessing and a curse. Much of it went, mysteriously, to Patterson’s brother-in-law, Al DeAtly, who used it to rescue his construction company, fashioning himself into the lead contractor in the state of Washington (where he built a country mansion as large and gaudy as Mar-A-Lago). But one of Patterson’s most loyal associates, Bob Gimlin (interviewed in the documentary), got nothing. That said, he is still on the Bigfoot convention circuit.

On the dark underside of the 59-second Bigfoot film lies a tawdry family drama. There is greed and infighting, all buried in the murk of a secret that must be maintained at all costs. Marq Evans uncovers the secret. He has assembled the documentary with resounding suspense, and he finds the smoking gun. It is a lost piece of 16mm film footage shot in 1966, the year before the famous Bigfoot footage, and what it shows is a kind of rehearsal for it. We also meet an associate of Patterson’s, a man named Bob Hieronymus, who has a familiar loping walk.

“Capturing Bigfoot” reveals that the 1967 footage of Bigfoot was a hoax, and in that sense you could say that the story is over and done with. Roger Patterson was a classic American snake-oil salesman who figured out how to con the media age. But one of the key themes of the documentary is that Patterson, with his ingenious little fake film, didn’t just create an outlandish legend. He created a reality that took on a life of its own. He created the “evidence” to make magical thinking real, and I don’t think it’s overstating things to say that you can draw a direct line from the true-believer world of Bigfoot to the true-believer world that so many exist in today, whether its UAP obsession or the wacked conspiracy theory that says the 2020 presidential election was stolen. Bigfoot or no Bigfoot, we’re all living on the Planet of the Ape Believers.