In the autumn of 1981, a young New Yorker named Jean Hanff Korelitz was studying at Oxford University when she was asked if she would like to be an extra in a movie called Privileged, a modern update of The Duchess of Malfi to the world of undergraduate theatre, directed by John Schlesinger.
She put on a dress, walked down to Rhodes House and found herself in a party scene with absolutely no idea what was going on.
The door opened and in walked the most beautiful young man she had ever seen, carrying a duelling pistol.
"I demand satisfaction," said Hugh Grant.
"He was stunning," Korelitz recalls, 40 years later, of the English actor who has just been seen in The Undoing, the glossy and addictive HBO adaptation of her 2014 novel You Should Have Known.
"You could tell as he crossed that room that he was going to be a star. He had so much charisma."
That charisma is what has kept viewers on both sides of the Atlantic nailed to their sofas on Monday nights for the past month to devour the thriller set in the chilly high-rise world of New York wealth.
Grant plays Jonathan Fraser, a paediatric oncologist whose carefully concealed affair with a mother at his son's elite private school suddenly bursts brutally into the life of his psychologist wife Grace, played by Nicole Kidman, when his lover is murdered.
Who killed Elena Alvez? Much like a young Hugh Grant, viewers have spent the past few weeks demanding satisfaction - and plastering their theories across the internet.
Korelitz (59) seems a little surprised when I ask her what she makes of the show's near-obsessive following.
She's speaking, she tells me over the phone, from a "very, very remote" part of upstate New York and, while she's on Twitter and Instagram, she informs me cheerfully, she doesn't "really understand the algorithm".
The result is that while she has "a weird feeling that something may be going on out there in the world", the hype around the show has left her largely untouched.
This means she has managed to remain innocent of the spoilers bouncing around the internet in the build-up to the final episode, which aired in the US the night before we speak.
"My son and I had a theory for who had done it, which turned out to be wrong," she tells me.
How is it possible that the author of the book didn't guess the ending?
Blame David E Kelley, the patron saint of gorgeous, starrily-cast yet somehow trashy dramas, most famously Big Little Lies.
It was he who took Korelitz's portrait of a woman whose perfect life suddenly implodes when her husband murders his lover and cranked up the thriller element.
On the page, the tension of the story resides in Grace's attempt to stitch her tattered life back together. On the screen, it's in the whodunnit.
Of course, as it turned out when the final episode aired, Kelley had double-bluffed us all: it was the psycho doctor all along.
Kelley steered the character away from Korelitz's original vision into Grant's comfort zone: Jonathan Sachs, the secular Long Island Jew, became Jonathan Fraser, the dry-humoured Oxbridge export.
Korelitz isn't bothered by the transition.
"I consider adaptation to be its own art form and I respect it. I'm not here to impede in any way," she says.
"I think David E Kelley is a genius, so even if I were inclined to, you're not going to interfere with Picasso."
She's also an Anglophile and has been a fan of Grant since that first appearance in Oxford.
"He's so cold in the part of Jonathan. Last night, there was one shot towards the end of the episode where there was nothing behind those eyes," she says.
"It really was a spectacular moment."
The character was inspired by an article Korelitz read years ago in New York Magazine's Best Doctors issue - a clipping of which can be glimpsed on the Frasers' bedroom wall in the show.
Something that one paediatric oncologist wrote somehow stayed with her.
"He said it was a privilege to be allowed into people's lives at their worst possible moment," she says.
"I thought, that's a beautiful sentiment - but what if you weren't a great guy?
"What if you were a person who's just drawn to that kind of intensity of emotion, not to mention the need to be the saviour walking into that room, the person who might be able to fix things, to heal your sick child?
"If you were the kind of person who perhaps wasn't very connected with emotions of your own, wouldn't you be fascinated by that kind of intensity?
"If you happen to be a sociopath, and you happen to be a doctor, you're not going to choose dermatology, you're going to want to go into a field where there's a drum roll every time you enter."
There's something particularly compelling about the spectacle of America's elite desperately trying to conceal its very dirty laundry.
"My son showed me this tweet from actress Issa Rae that said, 'Oh, I can't wait for tonight's episode of The Undoing. I love white people mess'," Korelitz says.
"You know, we all like to see the rich suffer a little bit."
Another attraction is undoubtedly the aesthetic: the hair, the clothes, those baroque Upper East side apartment interiors.
One Nicole Kidman coat in particular has broken the internet - a sweeping, moss-green number with a vaguely Pagan hood.
"I touched it once," Korelitz confides, like a guilty secret.
It was during one of her set visits, during which she nosed around the Upper East side locations and met Nicole Kidman's puppy, but nothing could beat that coat.
"It was chenille. It felt like a bedspread," she says.
As we slide into December, with no Christmas parties to look forward to, many fans of The Undoing will be daydreaming of a second series, Korelitz included.
"I would love it and I certainly have my own ideas, although I probably shouldn't say much," Korelitz says.
Where would she take the storyline, now Jonathan's villainy has been revealed?
"I think there's plenty more for Grace to confront. She's finally learned the big lesson about who she's been married to, so how does that impact every single one of her decisions about how to live?" she says.
David E Kelley, take note.