A heiress from the Big Apple revealed in her new book how her nearly two-decade-long marriage with her hedge fund executive husband imploded when she received a call from a stranger claiming he was having an affair.

Flobelle “Belle” Fairbanks Burden, the granddaughter of legendary New York socialite Babe Paley, initially declined the phone call from an unknown number, she revealed in the excerpt from her upcoming book “Strangers: A Memoir of Marriage,” which was published by the Times of London.

“I’m trying to reach Belle. I’m sorry to tell you this, but your husband is having an affair with my wife,” the shocking voicemail said.

At the time, in March 2020, the couple and their two youngest children had gone to quarantine at the start of the COVID-19 pandemic at their $7.5 million second home in Martha’s Vineyard, Massachusetts, when her husband Henry Davis’s hedge fund and Burden’s legal job had gone remote.

Burden, 56, confronted Davis, 60, about the reported infidelity, at which point, he allegedly admitted to the relationship with a far younger woman he met through work.

Davis allegedly insisted he was “embarrassed” about the affair and said it had only been going on for “a few weeks,” adding that it was “over” now, Burden wrote.

The mistress reportedly tried to take her own life when the relationship was exposed, Burden said, quoting a message apparently sent by the jilted husband.

“I think a month,” the mistress’s husband wrote, in response to a text Burden sent asking about the duration of the affair.

“But I can’t text because my wife has tried to kill herself. She’s in an ambulance,” the text continued.

The next day, Davis told Burden that he wanted a divorce, reportedly leaving without saying goodbye to his children, later calling to give a chillingly cold end to the marriage.

“I thought I was happy but I’m not. I thought I wanted our life but I don’t,” Davis reportedly told Burden. “I feel like a switch has flipped. I’m done.”

“You can have the [Martha’s Vineyard] house and the [New York] apartment. You can have custody of the kids. I don’t want it. I don’t want any of it,” he reportedly added.

Burden said she never got an adequate explanation from Davis as to why their marriage of 21 years had come to such an abrupt end, and then reportedly stopped taking her calls.

“I’ll answer what I want, when I want. I’ll speak when I want. I’ll decide when I want,” Davis reportedly texted Burden.

Davis’s family, after initially speaking with Burden, also suddenly cut her off, saying that they needed to support him, according to the memoir.

Today, almost five years later, Burden claims that Davis sees the couple’s three children only occasionally for dinners and tennis matches, but has not been involved in coparenting.

“There have been no handovers or holidays since the day he left,” Burden wrote, adding that she doesn’t know whether Davis is still with his mistress or whether he had any other affairs over the course of their marriage.

Davis did not respond immediately to requests for comment.