Part I of EW's epic look at this tale of six-guns and roses.

An immense shape, like a floating fortress in the mist, looms over the city. At times, it vanishes completely, masked by a curtain of seaside clouds.

When the midday sun breaks through, the gray cliffs and sky-scraping flattop resemble the ruins of impossible ancient architecture. This is Table Mountain, dominating the skyline of Cape Town, South Africa, and in its shadow, another monolith is rising — the film version of Stephen King’s The Dark Tower.

The six-guns-and-sorcery saga currently spans eight novels, comic books and short stories, and is woven throughout King’s larger body of bestsellers. It’s a genre mash-up of fantasy, sci-fi, westerns, horror, and mystery, set in a world — or worlds, plural — that are as endless as any built by J.R.R. Tolkien, George Lucas, and J.K. Rowling.

But really, the story comes down to something fairly simple, expressed in the opening line of King’s first book in the series, which will also open the movie: The man in black fled across the desert, and the gunslinger followed.

For those new to the tale, it’s largely set in a dimension called Mid-World, where the apocalypse has already come and gone — and now rolls toward our own like a breaking wave. For Constant Readers who are already steeped in King’s lore, director and co-writer Nikolaj Arcel’s movie (which debuts in theaters Feb. 17) will remix the novels much the way superhero movies often draw from decades of comics mythology to create a new cinematic origin story.

The same stones, but a different structure.

BEHOLD, A GUNSLINGER

Standing on the horizon of this otherworldly landscape is Idris Elba’s Roland Deschain — The Gunslinger — a frontier version of a medieval knight who is thirsting for revenge and haunted by visions of a tower that is surrounded by a field of dusky pink roses. He doesn’t fully understand what it means. No one does.

“When we meet Roland he’s a bit lost,” says Elba, sitting in the sun during a break from one of the movie’s dungeon-like sets. “He’s been walking around for a long time, so he definitely feels like a man who’s… coiled.”

In the parlance of King’s books, Roland “has forgotten the face of his father.” “That’s a sense of, ‘You’ve forgotten your purpose,’” Elba says. At the start of the film, Roland is driven by rage, but deep down he is something else. “He’s a protector,” Elba says. He just needs something to reawaken that part of himself.

Off in the distance is his quarry: Matthew McConaughey’s Walter, a.k.a. The Man in Black, a charismatic warlock who decimated Mid-World, is responsible for destroying everyone Roland loved, and is looking for more worlds to end. Bringing down the Tower is one way to end them all at once. (Learn more about him in part II of our Dark Tower coverage.)

Walter is searching for someone, too – a teenager named Jake Chambers (15-year-old Tom Taylor, in his first film role), who lives in our world and possesses “The Shine,” a powerful psychic ability that King readers should recognize backwards or forwards. Jake’s extraordinary magic could help Walter break the ethereal beams that keep the Tower standing and maintain order in the multiverse.

For Roland, protecting this boy could restore his nobility, putting him back on the path to protecting the Tower itself. “Until he meets Jake, he doesn’t have anything to believe in, really,” Elba says. “He’s really pent up and releases his soul through [defending] the boy.”

THE FACE OF A HERO

One obvious change from the novels is the fact that Roland has always been depicted as a white man with blue eyes, although to Elba that change is no deeper than a layer of skin.

As we sit outside his trailer, watching as the shape of Table Mountain vanishes and reappears in the mist overhead, we talk of Stephen King’s reaction to his casting, which was: “I love it. I think he’s a terrific actor, one of the best working in the business now.”

Elba smiles. Roland doesn’t smile much, but King’s words seem to nudge him.

“I was thrilled. I was thrilled to get this job,” Elba says. “I was thrilled because, you know, it’s an alternative to what you could say, what Roland is described as.”

I ask him if he means a white guy, and Elba shrugs. It’s more than that. “A white guy in a sense, but, also just that you could make a version of this film that appealed to a slightly more action-hero type character and I don’t do those films. I haven’t done many actions films,” he says. “I like to bring a little depth and bring a real character. And what’s been fun is, Nik’s really up for that. So we do takes that are a little bit more commercial, if you like, and we do takes that are f—ing deep, like we’re making an independent film. It’s an iconic character. I want to get it right.”

With Hollywood still struggling with diversity and inclusion, exemplified by the #OscarsSoWhite controversy this year, his casting in the role does seem to be freighted with extra significance. I asked Elba if he considers the race-swapping of the character to be a big deal.

“It’s better just to treat it like no big deal,” Elba answers. “There should be no difference. The character that was written in Stephen’s imagination, it could be any color. It just happens to be me and, you know? In the artwork, it just so happens to be a white guy, but I don’t think that makes any difference. … I think what’s great about it, if I want to say anything about it, is that it is a sign of the times in terms of a colorless society. People go, ‘A good actor is a good actor,’ you know?”

A SCENE OF STEALTH

Roland stands on a rooftop, the wind rustling his floor-length duster. A small camera and sound crew orbits him as he steps through a shattered window into a hallway, seeping with rainwater.

In the movie, this is the roof of the Dixie Pig, a way station in New York City where creatures from the nether can gather, disguise themselves as humans, and head out to prey. In real life, it’s Werdmuller Centre, a decomposing former shopping mall in southeast Cape Town, which has been converted into a hive of horrors for The Dark Tower.

The plaster stalactites crying droplets from the ceiling are real, but it’s hard to know if the graffiti smearing the walls is set-design or just another natural phenomenon of abandonment.

The actors lurking in the shadows ahead are Taheen, demonic, half-human creatures with animalistic qualities — but they are currently in our world. They disguise themselves as human beings with rubbery masks, but their true identities are given away by a scar-like red seam running down the sides of their necks.

As he ventures down the hallway, Roland emerges into a room dangling with what appear to be hundreds of scalps — the long clusters of hair drooping down and swaying in the breeze like spider legs.

Really, they’re just wigs the Taheen can choose from when they need to venture beyond the walls of the Dixie Pig. Thinking the Gunslinger is distracted by the strange sight, a fiend leaps from the corner and is promptly dispatched by a swing from the butt of Roland’s revolver. He doesn’t shoot. He’s not trigger-happy. His revolvers fire only when necessary.

“He’s just very efficient in that sense,” Elba says. “You know, if he can clear a room with five bullets as supposed to six, he will.”

From the Hall of Hair, Roland slips into another room as his infiltration of the Dixie Pig continues. This bare, concrete walled torture chamber has a single dentist chair in the middle, rimmed by a corona of blood. Whoever – or whatever – died here, died badly.

A doughy, middle-aged man (who is not really a man) mops up quietly. He has a thick red line running down one side of his neck. Roland is poised to draw, but sends the lowly monster scurrying with a single, unbroken stare instead. Very Eastwood.

This Taheen is not interested in tangling with a Gunslinger. Roland is the last of their kind, a group of warriors who wielded six-guns but were really guided by something else, something unknowable. Think of the spiritual side of a samurai – or the Force-sensitivity of a Jedi, from yet another galaxy altogether.

“There’s a mystical element to him,” Elba says during his break between scenes. “He’s about 200 years old. He’s been around for a long time, and has a deep-rooted connection with the [supernatural] nature of the film. Roland’s completely tuned into that. When you meet him, he’s very much a stoic man, doesn’t want to talk. But when you get to know him, he really knows quite a bit about the world and his world’s history.”

Elba stares up at the shape of Table Mountain, which has reappeared from behind the shifting morning clouds.

“And he very much knows the way The Man in Black works. He’s so clued up on that, which is what frustrates him,” the actor says. “Because he can’t catch him.”

For more on The Dark Tower, pick up the latest issue of Entertainment Weekly, on newsstands Friday, or buy it here — and subscribe now for more exclusive interviews and photos, only in EW.