It's a sunny morning in March in Charleston, South Carolina, the filming location of the Audience network's anticipated adaptation of the 2014 Stephen King novel Mr. Mercedes, but one would hardly know it from inside Prohibition Bar. With the windows covered and lights lowered, the 1920s-inspired speakeasy is transformed into a local Ohio Irish pub, McNally's Alley, where there's a moody encounter taking place between Janey Patterson (Mary-Louise Parker), a no-nonsense woman whose sister's Mercedes was used to kill 17 people three years prior, and Bill Hodges (Brendan Gleeson), a retired detective still haunted by the unsolved murders.

After two close-up takes on Parker, director and executive producer Jack Bender (Lost, Under the Dome) calls cut and huddles with the actress, who remains seated at the high-top bar table where Janey and Hodges are supposed to be absorbing the news that Hodges' computer has been hacked by the mysterious Mr. Mercedes killer with flirty, sexual subtext. It's a moment not unfamiliar to fans of hard-boiled detective stories, in which the brooding leading man is tantalized by a new woman in his life. (Janey even gives Hodges a black fedora, a nod to the gumshoe genre.) After a couple of hushed moments, Bender steps away and filming resumes. After the next take, Parker gets a nod of approval from the director and they move on to the next set up.

It's not that the scene wasn't working, the director says later during a lunch break in his trailer -- it just needed a few adjustments. "You just get greedy," Bender explains. While he considers himself a hands-off director, he does see himself as a conductor, giving tweaks -- "play this a little louder, a little softer" -- during filming. And with Parker, it's something he wanted to take full advantage of "because of how intuitive an actor she is. [The note] led to a slightly different adjustment for the scene." And it's perhaps those adjustments that will be key to the show's success.

Written by David E. Kelley (the Emmy-winning scribe behind HBO's hit adaptation of Big Little Lies), Mr. Mercedes tells the story of a dangerous game of cat and mouse as a demented serial killer, Brady Hartsfield (Penny Dreadful's Harry Treadaway), taunts a washed-up detective out of retirement with lurid letters and emails. Unsure who he's after, Hodges starts a private crusade to find the killer before he strikes again. In addition to Treadaway, Gleeson and Parker, the series stars Emmy winner Holland Taylor as Ida Silver, UnREAL breakout Breeda Wool as Lou Linklatter, Jharrel Jerome (Moonlight) as Jerome Robinson and Kelly Lynch (CW's 90210) as Deborah, Brady's demented mother with a much too close relationship with her son.

Executive produced by Kelley, Bender and King, who was so thrilled after seeing the first episode that he signed on to produce the 10-episode project, Mr. Mercedes, which premieres Wednesday, Aug. 9, is the Audience network's most anticipated (and high-profile) series. It follows AT&T's successful dip into original programming with Rogue, Kingdom (both of which ended this year), the throuple comedy You Me Her and Antoine Fuqua's Ice, starring Donald Sutherland. While the network is only available through DirecTV, Bender hopes that Mr. Mercedes will be the "one that stands out from the noise of the freeway" and that it will help make the network a destination for "more good material." The director also credits the network for supporting the team's creative choices in adapting the series, which includes casting Gleeson as the show's antihero.

‚ÄčThe biggest departure from the book is the transformation of Hodges, a Southern everyman, whom Gleeson gives a decidedly Irish touch with his snarling accent, hunched stature and reddish hair. While the 62-year-old actor has won an Emmy for his portrayal of Winston Churchill in the HBO film Into the Storm and appeared in Lake Placid (also written by Kelley), In Bruges and 28 Days Later, he's best known to American audiences for playing Alastor "Mad-Eye" Moody in the Harry Potter franchise. Outside of a failed pilot, Gleeson has not starred on a TV series.

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"I had a lot of soul searching about committing to the length of time," Gleeson says during a break in shooting, adding that the fact that there are only three books -- Mr. Mercedes is part of a trilogy, followed by Finders Keepers and End of Watch -- meant there was finite amount of storytelling. "There's a proper journey in there. There's a rise and a fall; it's not an endless kind of getting on a train and going off into somewhere." Of course, it didn't hurt that Bender and Kelley, whom the actor wanted to work with after appearing in Lake Placid, promised to be hands-on with the project. "I've worked on a situation before where there's a very good writer at the beginning, then it's handed off to people who haven't got it. It all gets very messy."

Ultimately thrilled with his decision to join Mr. Mercedes, Gleeson says, "There's only so far you can go before you have to take the jump. You never quite know and even with the best intentions some things fall apart, but it's been really great so far."

But any potential doubts were squashed with King's approval. "He's terrific in the part. I loved the casting ideas," the author says, adding that in addition to Hodges' character development, he likes Kelley's addition of one new character, Ida Silver, a nosy next-door neighbor and admirer of the former detective who is brought to life by Taylor.

The actress, who won an Emmy for playing Judge Roberta Kittleson on Kelley's hit legal dramedy The Practice, brings a lighter touch to Hodges' world. "There's so much darkness in him," Taylor says. "She's a decent person who cares about him. She seems kind of nosy, but she's actually concerned about him because he's gone terribly downhill since his retirement." Admittedly not a fan of horror or supernatural genres, Mr. Mercedes "is going to be a feast for Stephen King fans because there's one more devastating revelation after another," the actress says pointing to the real-life horrors -- cyber terrorism and vehicle-ramming attacks in Berlin, Jerusalem and Nice, France -- that have become even more prevalent in the three years since the book was first released.

MORE: Holland Taylor Talks Horror Genre, 'Mr. Mercedes' and Possibility of Working With Sarah Paulson

Initially concerned about the recent wave of terrorism, Denise Chamian, one of the show's casting directors, called Bender asking, "'How do we do this?,'" the director recalls. "And I said, 'That's a fair question, but given the world we're in right now, taking a look inside one of these monsters may not be such a bad thing.' And, tragically, I think we're going to see more of this." (In fact, two days after ET's visit to the set, a man drove a car into pedestrians walking along the Westminster Bridge in London, killing four people, before crashing his vehicle into the fence of the Palace of Westminster's grounds.)

While Bender points out that Mr. Mercedes takes place in a different world, that element of reality is something the director wanted to root the show in. "My MO is 'let's make it real,'" he says, explaining that there's style but it doesn't overtake the content. And with Hodges' fedora in mind, Bender adds: "We're tipping our hat to the genre without going too far."