RYE, N.Y.—“Marc is going to be another 40 minutes,” said Nick Newbold, popping his shaggy, baseball-capped head into the kitchen of a rental house in this leafy, yuppie haven in Westchester County on a Sunday afternoon in late September.

Marc is Marc Jacobs, who was hidden away in one of the home’s four bedrooms putting together his look for a portrait series that started back in June shortly after lockdown lifted in New York, when British Vogue commissioned a photo for its September issue.

It’s now become a ritualistic Monday morning Instagram post celebrating fashion, creativity and positivity. These days, Mr. Jacobs is all about lifting the spirits and being of service, as well as enjoying his own personal fashion expression in which gender norms are completely passé.

In one shot, he’s standing on a stool on the tennis court in a white shirt — no bottoms — black tights, pumps and a fedora. In another, he’s seated on the grass in a glamour scout get-up complete with park ranger hat (by Stephen Jones) and binoculars. “So Troop Beverly Hills!” the fashion writer Alexander Fury commented.

Part of the delay that Sunday, Mr. Newbold said, was the last-minute decision to use an open-toe shoe instead of a closed-toe pump, and Mr. Jacobs now had to do his own pedicure.

Mr. Newbold, a boyish 39, is the photographer on the portrait’s ad hoc crew of three, while Julio Espada, Mr. Jacobs’s former design associate at Perry Ellis, is the stylist. For a world-class designer, the setup is remarkably D.I.Y. “This is a ring light I literally got on Amazon for, like, $35,” said Mr. Newbold, whose only other equipment is a Sony camera and a tripod.

Yet the attitude on set has the professional conviction required for a high fashion editorial. Mr. Jacobs is not known to do things in half measures.

“Just a typical Sunday,” he said, emerging from his room in a bobbed wig parted to the side, his eyes aggressively coaled Cleopatra-style, with a silver streak at the corners. He was wearing a bespoke shirt, tie and shorts from his own label, a burgundy oversize cardigan by O’Connell’s, a cuff, belt and kitten heel sandals by Hermès, a bracelet and brooch by David Webb, earrings by Harry Winston, a pearl necklace by Mikimoto and, over his custom Marc Jacobs leather gloves, a pinkie ring by Solange Azagury Partridge. “Can you see the ring? Are you getting the ring?”

Mr. Newbold captured the boss posing in the den in front of the lit fireplace, his right leg extended balletically, foot perched on a small pile of birch logs. It would be posted to Mr. Jacobs’s 1.5 million followers the following morning with sappy lyrics from “Only Love Is Real” by Carole King. Everything is meticulously credited, including the photographer.

A Confidant and a Caretaker

Such access to Mr. Jacobs, who has long relationships with renowned photographers like David Sims, Juergen Teller and Steven Meisel, would be a coup for any aspiring photographer. For Mr. Newbold, who may be Mr. Jacobs’ most frequent and intimate collaborator, it was never part of the plan.

Neither a professional photographer nor striving to be, Mr. Newbold is Mr. Jacobs’s personal assistant. In the eight years since he’s been on the job, his duties have grown. He still walks the dogs, orders food and runs errands, but he also oversees things like his boss’s art collection.

“I’m buying everything, but sold it all, too, obviously with Sotheby’s,” Mr. Newbold said, referring to last year’s clearing house of Mr. Jacobs’s extensive collection, including works by Ed Ruscha, Elizabeth Peyton and John Currin, done with the auction house.

Mr. Jacobs offloaded these, and his Greenwich Village townhouse to make way for his new life in the burbs with his new husband, Charly Defrancesco. They married last year and promptly plunked down $9.175 million on a 6,000-square-foot Frank Lloyd Wright-designed house, which they are restoring with the architect’s conservancy.

In the meantime, the couple is holed up at a rented funky estate appointed with curious 1970s design relics — the mirrored powder room has a brown porcelain toilet. Mr. Newbold wrangled the property through Alice and Thomas Tisch, sellers of the Wright house. “I’ve done everything from demo old houses to get coffee,” he said.

Mr. Newbold now also sits in on packaging, production, merchandising and marketing meetings. “I don’t even know what his title is,” Mr. Jacobs said. “His title is Nick Newbold. He does a lot of stuff and he does all of it well.”

Mr. Jacobs added, “If you asked Eric Marechalle, the C.E.O. of Marc Jacobs International, how vital Nick is, he would tell you he values Nick probably above everyone. Nick is that whisperer that can understand what corporate needs and what creative needs and he’s able to filter the two and make it OK for both.”

More than a conduit, Mr. Newbold is a confidant and caretaker to Mr. Jacobs. He joins him and Mr. Defrancesco on vacation. On a trip to St. Barths a few years ago, Mr. Newbold filmed Marc, Char and friends in a Moke spoofing the orange mocha Frappuccino scene from “Zoolander,” which was the beginning of his unofficial role as Mr. Jacobs’s personal photographer.

He was ordained and officiated their wedding. “To say he’s like a brother to me or he’s like a father to me would be a terrible thing because my father’s dead and I’ve no relationship with my brother,” Mr. Jacobs said. “He’s what I wish for in a family member.”

Who is this guy?

“If you look back at my trajectory, I’ve always sort of said, like, ‘Yeah, why not?’” said Mr. Newbold, sitting in the deserted lobby of the Mercer Hotel on a recent Tuesday morning. Dressed in an army jacket, a sweatshirt that read “When We All Vote” (a collaboration between Mr. Jacobs and Dover Street Market), jeans and Vans, he brought his French bulldog Charlie, as well as two extra coffees, just in case someone else wanted one.

His path from civilian in New Hope, Pa. with no connection to or intention of a life in fashion, to the nexus of its star power and influence, was almost absurdly aimless. A self-professed autodidact and jack-of-all-trades, Mr. Newbold will “watch tutorials on YouTube and waste two days figuring out how to do something.”

He came to Mr. Jacobs by way of Christy Turlington Burns and her husband, Edward Burns, who hired him as their personal assistant in 2009 on the recommendation of their former nanny, a family friend of Mr. Newbold.

He ended up traveling the world with Ms. Turlington Burns, helping with her charity, Every Mother Counts, and accompanying her on marathons and shoots when she modeled. “He’s hardly a bodyguard, but he feels like someone who has your back,” she said in a phone interview. “Not in a gatekeeper way, in the most gentle, respectful way. He sort of just sets the tone.”

Before this, Mr. Newbold held a series of odd jobs: some public relations, a babysitting gig, designing a line of neckties, tiling Dunkin’ Donuts on a construction gig. He hated high school but said he had perfect attendance. He didn’t want to go to college but spent three years at Bates College before transferring to George Washington University for a woman.

He never wanted to live in a city, but here he is — 15 years in New York. “I’m a super-solitary person,” he said. “I’m alone all the time. I don’t like going out. Never have.”

He told his story in a soft-spoken ramble of guileless disclosure, bringing to mind the voice-over from the Dos Equis “Most Interesting Man in the World” commercials. Tangents abounded.

“You can have a conversation with him about one thing and then suddenly, he’ll just slip in, like, ‘Oh, and I used to race dirt bikes,’ or ‘I can drive professional, huge trucks,’” Ms. Turlington Burns said.

There was the time his band played CBGB in high school. The time he took up boxing and discovered the “sweet science” mental agility of it. The time he became a 100-mile a week runner, ending up a quarter mile from the finish line, he said, when the bomb went off at the Boston Marathon in 2013.

He fell asleep on his drive home and still showed up at work at 7:30 the next morning. Did he mention that he used to race stand-up Jet Skis? Or that his drone footage was used by Lana Wachowski in an episode of “Sense8”?

In July, Mr. Newbold went to St. Barths. “Guess who got dengue fever?” he said.

Confirming Ms. Turlington Burns’s account, Mr. Newbold said he drove a commercial truck delivering gelato from New York to D.C. He had an epiphany one night when he found himself pulled over at a weigh station with no commercial license and a broken taillight. “I was like, wait a minute, ‘I’m a truck driver now?’” he said.

He enjoys “disarming,” and sees his role at Marc Jacobs as “a fixer for everything.” It inspired his Instagram handle, @1.800.Newbold. Got a problem? Call Nick.

Mr. Newbold has always been attracted to off-the-beaten-path creative people, he said. But “I never allowed myself to be creative.”

A cynical mind may wonder, is his meander actually a climb?

“Nick’s one of those people I’ve never tried to figure out or analyze. I trust him,” Mr. Jacobs said. “So I’ve never delved deep into any facet because I tend to do that when I think somebody has got an angle, and Nick to me, from Day 1, I never felt he was in this for something other than the very honest and immediate reaction that he had.”

Ms. Turlington Burns said: “He’s also not someone who’s incredibly ambitious.”

In Mr. Newbold’s own words, “I don’t have goals.” Rather, he rises to the occasion.

Good in Disasters

When the coronavirus hit New York, Mr. Newbold was ready. “I’m such a steady, even-keeled person,” he said. “Marc and I really bonded over Sandy” — the hurricane — ”because his house flooded. I was there. I had only known him for a couple months at that point. Literally, the water was at my knees, and I’m still grabbing stuff. Then, I heard the door was about to bust open. That was crazy. In disasters, I’m good.”

Even without Sandy, Mr. Newbold said he and Mr. Jacobs have “been to hell and back” together, bonding during the end of Mr. Jacobs’s 16-year stint as creative director at Louis Vuitton, the ouster of his longtime business partner Robert Duffy from the company, and a carousel of restructuring, reseizing and business ups and downs. And then the pandemic.

“I was so prepared when it happened,” Mr. Newbold said. “I was ready to bug out. Marc could tell you. It’s like, ‘Well, Nick’s ready to go anywhere.’ I was like, ‘I have passports, we have cash, I have a car. I know where to go.’”

The furthest they got was the Mercer Hotel, where Mr. Jacobs spent 70 days as one of three residents at the hotel. (Mr. Newbold maintains his own apartment downtown.)

At the suggestion of Sofia Coppola, one of Mr. Jacobs’s close friends and collaborators, Mr. Newbold took out his Sony a7ii hand-held camera and began chronicling the surreal experience of one man living in an all-but-deserted hotel with a staff of four.

“I couldn’t believe how long Marc was staying at the Mercer and that it was just a few of them there,” Ms. Coppola said. “I was like, ‘I hope you’re filming this.’”

A 28-minute film titled “A New York Story” resulted, falling somewhere between documentary and humorously bizarre art house piece, beginning with Mr. Jacobs checking in and ending with him checking out and driving off with his husband when the lockdown is lifted.

Mr. Jacobs plays every character in the film: the concierge greeting himself at the front desk, the bouncer at the hotel’s club the Submercer, where he goes for a drink (Diet Coke) on Saturday night, the maintenance person he summons to the room to change a light bulb in one of the film’s more subtly funny moments.

It’s one thing to know that Mr. Jacobs is a mere mortal, but it’s another to imagine him ordering Seamless, making his bed, operating an espresso machine or changing a light bulb. “That’s the one thing Marc won’t do,” Mr. Newbold said.

The narrative is the last man in the city at a vacant hotel, “going in with one mind-set and coming out with another,” Mr. Newbold said. Mr. Jacobs left his room only to shoot the scenes for the film. There’s also a strand of pearls that the designer wears in every scene. Make what you will of it.

Ms. Coppola gave editing notes. Bill Sherman, the composer known for his work with Lin-Manuel Miranda, as well for being the musical director of Sesame Street, did an original score.

The film can be seen on Mr. Newbold’s YouTube channel. It doesn’t promote the Marc Jacobs brand, at least not directly — the designer styled himself in a combination of hotel uniforms and his own clothes. If anything, it underscores Mr. Jacobs’s need for creative outlets under any circumstance. “An artist needs to create,” Mr. Newbold said. “Otherwise what else is there?”

What did Mr. Newbold get out of it? Another task mastered. “The funny part is, I don’t really want to share this,” he said of the film. “I’m happy we did and that’s enough, but Marc and I were chatting the other day. He loves to share. He talks about the importance of sharing experiences and art as part of the process. Even the little videos I do for Instagram. I don’t really post them on my Instagram, Marc posts them. He’s the vessel.”