By the time Ghislaine Maxwell was fighting allegations that she had procured underage women to provide sexual services for her ex-boyfriend Jeffrey Epstein, there was a new man in her life.

His name was Scott Borgerson. Ms. Maxwell, according to her friend Christopher Mason, described him sometime around 2015 as a “Navy SEAL,” though he was actually a former Coast Guard officer.

It didn’t exactly surprise Mr. Mason (or others she described Mr. Borgeson to in the same way) when this fact came to light. Ms. Maxwell had always been known among her friends as a person with a singular ability to mythologize her own reality.

In an effort to rebrand herself from jet-setting cosmopolitan to oceanic conservationist, Ms. Maxwell had in 2012 founded and appointed herself C.E.O. of the TerraMar Project, an opaque organization that had no offices and gave no grants to other organizations. It was disbanded in 2019.

Its biggest accomplishment was helping Ms. Maxwell maintain social capital. Associating herself with Mr. Borgerson — the founder of a maritime investments company called CargoMetrics and a former fellow in residence at the Council on Foreign Relations, where he wrote about oceanic issues — added to her credibility.

Mr. Borgerson was called a director at the TerraMar Project, although he never had a job there. Ms. Maxwell supplied him and CargoMetrics with introductions to people on her contacts list.

When Mr. Epstein died from an apparent suicide while in jail in 2019, Ms. Maxwell became a subject of intense public interest: Why, given the volume of accusations leveled against her by women who said they had been abused by Mr. Epstein as minors, had she been able to avoid charges? Where was she hiding? How did a self-possessed woman of immense privilege come to be involved in the sex trafficking of teenage girls?

A year later, on July 2, Ms. Maxwell, 58, was arrested in New Hampshire by agents from the Federal Bureau of Investigation and charged with conspiring with Mr. Epstein to sexually abuse minors. At a bail hearing shortly afterward, Ms. Maxwell pleaded not guilty. Prosecutors in the case also dropped a bombshell: Ms. Maxwell said to them that she was married but would not divulge the identity of her spouse.

Speculation immediately turned to Mr. Borgerson, 44, although no record has been found of any marriage. Mr. Borgerson (who did not respond to two interview requests) has denied dating Ms. Maxwell, saying repeatedly that they were “friends” and that he didn’t know where she was.

But according to two friends of Ms. Maxwell who asked to remain anonymous because of the furor surrounding the allegations around her, Mr. Borgerson and Ms. Maxwell began sharing a 6,000-square-foot, five-bedroom home in Manchester-by-the-Sea, Mass., after Ms. Maxwell sold her 7,000-square-foot townhouse on the Upper East Side for about $15 million in 2016. (That was the same year she struck confidential settlements in civil court with two women who said she participated in Mr. Epstein’s sexual exploitation of them.)

In December 2019, prosecutors say, she used an anonymous L.L.C. called Granite Realty to buy a mansion in Bedford, N.H., in a $1.07 million all-cash deal, about an hour away from the home she shared with Mr. Borgerson.

Recently, Mr. Borgerson was photographed walking a dog that friends of Ms. Maxwell’s recognized as her champion-bred vizsla. Publications around the world staked out his home.

According to a 2016 profile in Institutional Investor, Mr. Borgerson grew up in rural Missouri. His father was a former Marine infantry official, and his mother taught high school French and Spanish.

The family was Presbyterian, and Mr. Borgerson told the publication that in high school he considered becoming a priest before deciding instead to attend the U.S. Coast Guard Academy.

“There’s a lot that motivates me, including — if I’m honest — I have a big chip on my shoulder to beat the prep school, Ivy League, M.B.A. crowd,” he said. “They’re bred to make money, but they’re not smarter than everyone else; they just have more patina and connections.”

Not that his own education was shabby.

In 2001, he enrolled at the Fletcher School at Tufts University, where he earned an advanced degree in the arts and diplomacy.

After that, Mr. Borgerson taught history at the Coast Guard Academy for a few years.

In 2007, he became a fellow in residence at the Council on Foreign Relations, a think tank whose officers and directors have included Colin Powell; the philanthropist David Rockefeller; and Robert Rubin, the secretary of the Treasury under President Bill Clinton. While at the the Council on Foreign Relations, Mr. Borgerson wrote for a magazine it publishes called Foreign Affairs about the effect of global warming on the Arctic region.

His residency as an International Affairs fellow ended in 2008, a spokeswoman for the organization said, and Mr. Borgerson spent another two years as a Visiting Fellow for Oceans Governance, working offsite.

In 2010, he founded Cargometrics, a “maritime innovation company” that uses data systems to study shipping patterns, from which the company determines what goods are being sent where and in what quantities and then bases investment decisions on the results. (For example, in February of this year, the firm used its data on cargo from China to surmise that imports from there were “in free-fall” because of the coronavirus.)

Back when Mr. Borgerson was writing for Foreign Affairs, there weren’t a lot of articles being published about oceanic conservation, said Dagfinnur Sveinbjornsson, the C.E.O. of the Arctic Circle, an organization dedicated to economic and environmental issues in the region.

Mr. Borgerson’s were “among the most prominent,” he said in an interview. “That’s what led to his involvement in the Arctic Circle.”

Mr. Borgerson was picked to serve on its advisory board and moderate a discussion about “Business in the Arctic” at the organization’s annual assembly in Reykjavik, Iceland, in 2013.

Conferences are a strange business. Big issues are often on the agenda, but the events can also (in prepandemic times) serve as glorified cocktail hours and public relations opportunities for people seeking to make connections and enhance their reputations as philanthropists, whether or not they even have a substantial record of working on the causes they’re discussing.

This category included Ms. Maxwell, who spoke at the Reykjavik conference and did not have the organization’s endorsement, according to Mr. Sveinbjornsson. According to British tabloids, it was there that Ms. Maxwell made the acquaintance of Mr. Borgerson.

He was the father of two young children with his wife, Rebecca, to whom he had been married since 2001, public records show.

In 2014, he filed for divorce, citing irreconcilable differences. Ms. Borgerson obtained a restraining order from Mr. Borgerson. (It was later dismissed.) In legal filings, she claimed that he drank too much, hit her and threatened to beat her in front of the children.

Ms. Maxwell was smitten with Mr. Borgerson, stating over and over again how “hot” and “brilliant” he was, according to a person who worked with the TerraMar Project and agreed to speak to The New York Times on the condition of anonymity, concerned the association would draw censure from environmentalists.

Ms. Maxwell also described the relationship between Mr. Borgerson and his ex-wife to this person as having become cordial, adding that much of her life now involved making lunch for his children and driving them to school.

After Mr. Epstein’s 2019 indictment on sex trafficking charges, the enormous interest in Ms. Maxwell led reporters to Mr. Borgerson, who admonished them for peddling gossip.

They would be far better off, he said, writing about the Jones Act, an esoteric maritime regulation from 1920 that stipulates that all ships on the water traveling between United States ports be built on United States shores and be owned by United States citizens. (It has recently become a point of contention between economists who see it as senselessly protectionist and others who contend that it is essential to preventing terrorism.)

Many of Ms. Maxwell’s old friends were surprised to read in reports of court proceedings earlier this summer that she had gotten married. It remains possible either that she was not telling the truth or that her spouse is someone other than Mr. Borgerson.

Brendan Hammer, a divorce lawyer in Chicago, said it was certainly “a little strange” that no records of a marriage have yet been found in widely used databases. But there could be various explanations, he said, like the ceremony taking place abroad, or paperwork delayed by the pandemic.

Of course, there are reasons aside from love for a person facing the prospect of a criminal indictment to get married, said Jeffrey Chabrowe, a prominent defense lawyer who previously worked as a prosecutor in the Manhattan district attorney’s office.

One is that spousal privilege can prevent prosecutors from compelling a husband to testify against his wife. Second, he said, “it makes moving money around much easier.”

This would be advantageous if Ms. Maxwell pleads guilty to any crimes or gets convicted of sex trafficking. If that happens, said Mr. Chabrowe (who, like Mr. Hammer, is not working on Ms. Maxwell’s case), she will likely have to deal with numerous civil suits from victims of Mr. Epstein who say she facilitated his crimes.

“Not only does it mean the civil cases likely ramp up, but new ones likely emerge, because there’s blood in the water,” Mr. Chabrowe said. “Epstein is gone, so they’re going for her. ”