Behind closed doors and papered-over windows, a half-dozen storytellers have been scrambling to conjure a fantasy world with compelling characters, fierce dialogue and an intricate plot. But this is no ordinary writers’ room: It’s Telltale Games, an independent video-game studio that has developed an intense following by prizing nuance and narrative in an industry more often associated with clattering machine guns and screeching getaway cars.

Considered by some to be the “HBO of gaming,” Telltale has set itself apart by adapting popular books, movies and television shows — “Back to the Future,” “Jurassic Park” and “The Walking Dead” — into adventure games released as short, episodic chapters that can be downloaded for $5 each. This model taps the same slow-burning qualities that have made prestige television dramas so popular and allows Telltale to work on multiple projects for less money than some companies might spend on games that sell for $60 a copy.

The studio, based in San Rafael, Calif., recently has turned considerable attention to the next big name on its roster, a video-game version of the epic fantasy series “Game of Thrones,” now in Season 4 on HBO. The character development and sense for story that sold HBO on a deal with Telltale are time-tested qualities, no matter the format.

“There’s a reason we’ve seen this strategy emerge in media again and again over the years,” said Katherine Isbister, director of the Game Innovation Lab at the Polytechnic School of Engineering at New York University. “Human beings enjoy being in the thrall of an ongoing saga. It allows us to get to know a world and characters over time and gives us a chance to reflect and discuss.”

While producing the “Game of Thrones” game, which is due this year, Telltale also is working on the second season of “The Walking Dead” and on “The Wolf Among Us,” based on Bill Willingham’s “Fables” graphic novels.

“We’re solving problems on a story level that other game companies don’t even realize are problems,” said Dan Connors, co-founder of Telltale. “We’re approaching this like it was a film or television series.”

Connors created the company in 2004 with Kevin Bruner after they left LucasArts, the video-game publishing arm of Lucasfilm now owned by Disney. They wanted to make games as exciting as television — to have people debate them with as much enthusiasm as they did for a show like “The Sopranos.” The challenge with each project is to avoid alienating an established fan base.

Telltale’s first episodic series, “Sam & Max Save the World,” was released in 2006 in monthly installments. This was followed by games based on “Strong Bad,” “Wallace & Gromit,” “Back to the Future” and “Jurassic Park.” The biggest success came in 2012 with “The Walking Dead,” adapted from Robert Kirkman’s comic books and the hit series on AMC.

Caring about zombie killers

Telltale executives would not comment on the studio’s financial position, but before the premiere of “The Walking Dead,” Steve Allison, the company’s senior vice president for publishing, predicted that the game could become a $30 million franchise. Telltale now says it “surpassed expectations,” selling 1 million copies in the first 20 days and more than 28 million episodes to date. The game has won more than 100 industry awards.

The appeal is tied to the game’s ability to make players care about the characters. The five episodes in the first season of “The Walking Dead” end on cliffhangers, and scenes become increasingly intense. (One memorable scene has the player cut off the main character’s arm after a fatal zombie bite.)

“It resonated with people,” Connors said. “It immersed you in the world and allowed players to create relationships with characters in a way they’d never done before.”

Telltale relocated to San Rafael from a smaller office near San Quentin prison. There is a studio on one floor, production space on another and a sun-drenched deck overlooking the Marin County countryside. The staff has doubled every year since 2012, to around 200 employees now.

Amid that growth, Bruner and Connors felt confident enough to pursue something they considered even bigger than “The Walking Dead.”

“We’re giant interactive storytelling dorks, and we’re giant ‘Game of Thrones’ dorks,” Bruner said.

‘Winter is coming’

But Telltale leaders knew they would need more than résumés to persuade HBO. Some previous forays into gaming had not met with much success for HBO: A 2006 game based on “The Sopranos” received poor reviews, as did a 2012 role-playing game based on “Game of Thrones.”

Telltale had to make the case that its game would pay as much attention to narrative and characterization as the show and that it wouldn’t be a cheap knockoff involving the kings and queens of Westeros running around collecting coins or hacking off one another’s heads.

HBO executives asked for a “Thrones” prototype, so Telltale produced a 10-minute presentation of what its version might look like.

“We were struck by the sophisticated level of work and high-quality approach to storytelling in all of their games,” Josh Goodstadt, the vice president for global licensing at HBO, said by e-mail. “We quickly recognized that this same level of quality and dedication could be a great complement to the richness of ‘Game of Thrones.’ ”

Telltale has a story consultant assigned by HBO, Ty Corey Franck, a science-fiction author and the personal assistant to George R.R. Martin, author of the books that inspired the TV series and an executive producer on the show. Much work remains before the game has its premiere, and no one at Telltale seems eager to publicly reveal more details.

A room for brainstorming is off-limits to visitors. There’s a “Do Not Disturb” sign on the door, and muffled voices can be heard inside. On a recent day, a pink sticky note joined several dozen others visible through the glass. For all the mystery surrounding the project, it appeared that progress was being made.