Production designer Jack Mossa has his own version of a nightmare. 

It recurs every time the boss, Ryan Murphy, comes to inspect his work on “American Horror Story: Cult,” airing on Tuesdays. The show takes place largely in a couple’s carnivore-friendly restaurant and the upscale home where their young son’s comic books, featuring vicious clowns, may be coming to life.

Will Murphy warm to the copper-accented stove in the kitchen? Savor the slabs of meat hanging in the cooler? Throw cold water on the antique bathtub?

“When Ryan walks on the set, I’m prepared for two things,” said Mossa while maneuvering between tables in the bistro last month. “One, a deep sigh of relief and everyone’s patting me on the back except Ryan. And two, me packing up my office and going home.”

Murphy may be heralded these days for resurrecting the careers of aging actresses like Jessica Lange and Kathy Bates, but the stars wouldn’t shine if he didn’t pay just as much attention to the settings, whether it’s Joan Crawford’s tufted, plastic-covered furniture in “Feud: Bette and Joan” or the walkway leading up to the Brentwood mansion in “American Crime Story: The People v. O.J. Simpson.”

For “American Crime Story: The Assassination of Gianni Versace,” set to premiere in early 2018, Murphy insisted that his crack research team chase down the most trivial of factoids: the backpack and shoelaces favored by killer Andrew Cunanan, the ashtray where Versace stashed his keys, the orchid plant on his dining room table.

“Detail is everything,” said producer Alexis Martin Woodall, who has worked with Murphy for a decade. “If you have to stop in the midst of a great moment because you’re looking at the artifice, then we’re not doing our job. Every bit of polish has to be there so the minute you hit ‘play’ or turn on the TV, you’re in it. We’re all obsessive about that.”

With at least three series in production at any moment, Murphy doesn’t have time to personally sweat over every prop and color scheme. He’ll meet with department heads months before the cameras roll, offer general notes and then have his team report back with miniature models and storyboards a few weeks later. Even after the sets are up, Murphy still must give his stamp of approval — and a thumbs down can come at any time.

Mossa, for example, had to pull a driftwood sculpture in the “Cult” living room because Murphy decided it didn’t fit.

“He makes decisions very quickly, which I find great,” said set designer Judy Becker, who is overseeing the look of “Versace” and whose work on “Feud” is up for an Emmy. “I don’t take things personally. If he doesn’t like something, I’ll say, ‘Fine,’ and find something else. It’s the people who are indecisive that are hard to work with.”

For “Versace,” the film crew shot scenes at the designer’s home in Miami Beach, capturing his lavish swimming pool (now part of a hotel). Becker made sure that the decorated picture frames in his hallway mimicked Versace’s taste.

Film crews won’t actually shoot in Minnesota, where Cunanan’s killing spree began, but they scouted areas of Los Angeles that could double for downtown Minneapolis and screenwriter Tom Rob Smith pored over 400 pages from Twin Cities police reports to help shape the interior scenes featured in two of the 10 episodes.

Being detail-oriented doesn’t always mean historically accurate, however. Becker and Murphy took liberties in reproducing Versace’s Milan workplace.

“He and (his sister) Donatella worked in a bare white space. We felt we had to improve upon reality to make it interesting to a TV audience,” said Becker as she showed off the Italy-based set, which is so swank it could double as a nightclub. “In ‘Feud,’ Hedda Hopper really lived in a ranch house. That wouldn’t have looked good on-screen. I like to know what reality is and then we can decide whether to go with it or not.”

That philosophy may not win Murphy and company any hurrahs from historians, but it’s made his shows catnip to viewers. In addition to “Cult” and “Versace,” he’s developing miniseries about Hurricane Katrina and Princess Diana’s divorce.

Expect the details to be dazzling.

“That, to me, is one of the joys of the work,” Murphy said.