If you’ve been watching HBO’s latest limited series “The Third Day,” then you’ve undoubtedly heard talk of a very special upcoming festival. The show’s lead, Sam (Jude Law), may have stumbled upon the island by accident, but everyone else — from his visiting bunkmate, Jess (Katherine Waterston), to the oddball locals Mr. and Mrs. Martin (Paddy Considine and Emily Watson) — are busy preparing for Osea’s annual autumnal celebration. Travelers come from far and wide to stay at the inn or camp out under the stars, dance around bonfires and consume untoward amounts of ale (among other things), all to honor the island’s ancient cultures (which, of course, are long dormant and are definitely not still operating in creepy, cult-like earnest).

Think of it like Burning Man, but for history buffs. Or “Midsommar”-lite.

Best of all, rather than merely watch the festival in the background of another episode, fans will be able to take part in an immersive live event dedicated to the music festival itself. Created by the immersive theater company Punchdrunk, “Autumn” will be co-directed by the company’s founder Felix Barrett and “Summer” episodes director Marc Munden. Jude Law will appear, and a release date has been set: Saturday, October 2. What else is in store? Well, IndieWire spoke to Barrett, Munden, Law, co-star Katherine Waterston, writer Dennis Kelly, and more collaborators on “The Third Day’s” ambitious event to provide everything you need to know in advance.

Read on for further details, and don’t worry: All this cult-y insanity can be enjoyed from the safety of your own home. No blood oath required.

So What Is This, Exactly?

Titled “Autumn,” the live episode (or live “immersive event”) falls squarely between the “Third Day’s” two seasonal parts: The first three episodes make up the “Summer” section, and star Jude Law. These episodes have already aired, so they serve both as the lead-in for “Autumn” — as well as the lead-in for “Winter,” the limited series’ final three episodes featuring Naomie Harris.

Though the live episode is set in the middle of the story, it was actually the basis for the series itself. Long before the pandemic hit, Barrett went to meetings with various collaborators asking, “How do you do theater on the screen?” And one of those meetings was a rather informal encounter with an old friend.

“So, I know Felix from school days,” Law said. “Then we reconnected when I became a big fan of Punchdrunk — I saw a lot of their early productions [and] eventually realized that Felix was the Felix I remember from school days, and we became friends again. Then about seven years ago, I’d probably been crass and overtly emotional and enthusiastic — as I can be sometimes, especially if I’ve had a glass of wine — and I probably said, ‘I want to be in one of your plays.” So he came and pitched me this idea of this cross-medium concept, whereby a piece of film storytelling would turn somehow into a piece of immersive theater. And I was just, ‘Yeah, yeah, yeah, yeah, let’s do it.’”

Punchdrunk is the company behind immersive theater projects such as Sleep No More, an award-winning adaptation of “Macbeth,” and “Believe Your Eyes,” which incorporated VR into its Cannes production. For “The Third Day,” the company aimed to bridge the gap between a live experience and an ongoing TV series.

“There’s something interesting about a story transcending the media you’re telling; how you can actually be watching a TV show and then the fourth wall of the screen can fall open and you fall inside it,” Barrett said. “Then the story passes back into television to wrap it up.”

With that live aspect as a starting point, creator Dennis Kelly said they then started fleshing out characters and story. But it wasn’t until they found their setting that the whole project clicked into place.

“Then Felix found Osea, and once we got Osea, it really started becoming clear what [the series] should be,” Kelly said.

Osea Is Real?

Yes! Osea is an island off the eastern coast of the United Kingdom that’s less than a square mile in size. Part of what makes the location unique — and what’s become a key plot point in the series — is Osea’s causeway, a road that connects the small island community to the mainland, but floods intermittently and thus strands visitors like Sam. (Per Google Maps, you could walk the mile-long causeway in less than 20 minutes, shore to shore, but let’s not get hung up on that.)

This eerie yet natural occurrence was originally supposed to play more of a factor in the live event as well. “Autumn” was supposed to be a live, in-person event.

People Were Going to be in Osea?

Original plans were to invite fans to visit the island themselves, with trained performers, functioning sets, and live musical acts all working together to create a lived-in version of Osea music festival. (HBO actually created a similar event for “Westworld” at the 2018 SXSW Festival.)

“We were gearing up for the 10,000[-person] festival that you’ve seen alluded to in Episode 1,” Barrett said.

Then the pandemic hit, and it became clear such a large gathering was no longer feasible.

“Safely, you can only get 20 in the audience,” Barrett said. “So, from 10,000 [people] to 20 — I mean, it’s not much of a music festival.”

Barrett and Kelly got together to try to find a new way forward. Pivoting from an in-person theatrical experience wasn’t as simple as just deciding to livestream what was already planned. After all, not only was it unsafe for all those fans to attend, but hiring a fleet of extras to recreate a rollicking festival atmosphere wasn’t an option either. They had to tweak the story leading up to “Autumn” for a more intimate event.

“The community will decide not to do the festival. They’ll close the causeway,” Barrett said. “It would just be the same as they’d done in previous years where they will have their own insular little festival with their own traditions. And instead [of a live audience], we’ll put a camera there — the audience of one — for a continuous, 12-hour Steadicam shot floating around. So, it becomes like an outside eye observing the sort of ethnographic [study] of this community on their most holiest of days.”

Wait, it’s how long?

Twelve hours. On Saturday, “Autumn” will stream from 4:30 a.m. ET until roughly 4:30 p.m. ET, give or take a few minutes for diversions, mishaps, or otherwise unforeseen alterations to the schedule. (An exact start time is “all tide dependent,” per Munden). This timing was chosen because the event will be shot on location, in Osea, in the U.K. (with a sizable U.K. audience to consider), but “Autumn” will be easily accessible for American audiences via HBO’s Facebook page.

Part of the length is attributable to the episode’s “slow cinema” approach. Otherwise known as “contemplative cinema,” slow cinema is often non-narrative, and the people behind “Autumn” said the unbroken one-take required a change of style. After all, it’s not like Sam can realize he needs to talk to Jess, and then the episode cuts to them chatting; the live episode will also have to show him walking to find her.

“When the live [element] changed [to a virtual format], I was like, ‘Well, we should do it like a 12-hour installation,’ director Mark Munden said. “We could just watch the tide come in for an hour-and-a-half, or we could watch one of our actors waiting for something, or we could follow behind their head as they walked from the causeway all the way to the village’ — things like that. We’ve got this great opportunity to do things that you could never do on television because of the durational aspect of it.”

Do I Need to Watch the Whole Thing to Understand the Rest of the Series?

No, but the live episode offers benefits beyond linear clarity.

“Because we thought people were physically going to the island, we designed the series so that you could watch it without connecting to the live event,” Kelly said. “But if you do connect to the live event, you will get a lot more. There are story threads within the series that are only really answered on the live stream.”

Barrett also promised there will be “clues and things” tucked into the live event, but more specifically, “Autumn” will delve into Osea folklore and mythology. Have you been wondering about the ritual sacrifices? Or their pagan gods? Or any of the other strange (read: frightening) island oddities that have popped up in the first three episodes?

“That’s the main thing,” Mylod said. “It allows us to see what we’ve heard of this mythology of the island in a very real way, and acted [out] in the way that we see old pagan ceremonies still being re-enacted in Britain, whether it’s the Hastings and the Lewes Bonfire societies, or whether it’s tar barrel rolling, or all that sort of stuff.”

Barrett pointed out that using a live, unbroken shot helps “blur the boundaries between what’s real and what’s fictional.”

“As soon as it’s happening in real life, it’s almost as though the narrative veil is lifted,” Barrett said. “We hope it becomes a sense of urban mythology and you start to think, ‘Wait a second, do they actually really do this at this place?’ And then once you Google it, you realize actually 80 percent of the folklore is real.”

Barrett said they brought in designers and researchers to help establish the cultural elements that make up this fictional Osea community’s history.

“We’ve gone extremely deep,” Barrett said. “We want it to feel plausible. […] As religion traveled around the world, it’s evolved. So we’ve created our own fictional one that’s built on stuff that’s familiar, so it feels like it’s plausible and yet it is our own creation.”

Will the Live Episode Connect the “Summer” and “Winter” Stories?

Not exactly. In fact, the live event helps to break up the limited series and better distinguish its part.

“Rather than a series and a live event, it’s actually three things,” Kelly said. “It’s Summer, Fall, and Winter. Summer and Winter are really quite different in time and feel. We have two different filmmakers making them. When Naomi comes in [for Episode 4], it’s got a really different feel. It’s got a different director of photography, it’s got a different composer, and a different director.”

Munden directed the first three episodes, introducing “The Third Day” as an alluring dream-state. Sam often awakes from disturbing nightmares that begin as if they’re part of his reality, and Episode 3 even features a drug trip that sees Sam and Jess flying off into the night sky. It’s fantastical, even when it’s truthful. But the “Winter” set of episodes — helmed by Philippa Lowthorpe — are stark and unflinching. Lowthorpe utilizes stationary framings and smooth transitions rather than Munden’s roaming, disconnected camera.

“‘The Third Day’ is about those filmmakers as much as it’s about anything else,” Kelly said. “It’s about them bringing their own visions of these two different [parts]. The whole thing makes one big whole and the story hopefully ties together, but they are kind of individual parts, and in some ways almost standalone.”

With all that work going into each scripted part, the live episode had to find its own distinct look and tone, as well.

“It’s a completely different flavor to the TV show,” Barrett said. “The [series] is brilliantly made, contemporary television. This is live theater meets slow cinema. And it’s 12 hours — with Jude and Catherine in character for 12 hours, living those parts with no backstage, no greenroom, no, ‘We’re going to go again.’ It’s one take, and that’s it.”

So Jude Law and More of the Cast Are Part of the Live Episode?

Yes! Though it’s unclear how much screen time each actor will have, both Law and Waterston are performing in the live event.

“There were definitely challenges ahead of me and the live event was always — not unknown, but had this sense of danger,” Law said. “Even when it was a 12-hour event with thousands of people, now it’s a 12-hour event with God knows how many people watching you on a camera.”

Waterston said the show would’ve been enough for her to sign on, and at first, that’s all she knew about.

“I read it, and then I talked to Mark, and I think Mark started to explain to me what this live element would be,” she said. “It was like this really spectacular cherry on top. The show was already interesting on its own, and then there’s this wild experiment that we’re going to do with it.”

Law said the audience can feel the danger during most of Punchdrunk’s immersive theatre, and he hopes that energy will translate to this streamed event.

“Watching someone sleep, or eat their lunch, or staying with them — whether it’s on the back of their head or the side of their face for a 20 minute walk — or, of course, going through some of the rituals that that will be thrown at us on the day, I hope that there’s a sense of emotional connection,” he said. “And I hope that because of this sense of a shared experience, that [there’s an] electricity that will bond us a little more. I hope that draws people in more.”

I’m In. How Do I Watch It?

“The Third Day” live episode will begin streaming Saturday, October 3 at 4:30 a.m. ET on HBO’s Facebook page. The event will also be available to view in its entirety after the initial broadcast. “The Third Day” Episode 4, “Monday – The Mother” premieres Monday, October 5 at 9 p.m. ET on HBO. The series finale is slated to premiere Monday, October 19.

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