On a quiet summer morning, a body washes up on a Nantucket beach. A scream splits the air — and a prominent family is immediately plunged into chaos.

So ends the first episode of Netflix’s soapy drama series “The Perfect Couple,” based on the novel of the same name by bestselling author Elin Hilderbrand. Developed for the screen by showrunner Jenna Lamia (“Good Girls”), the show follows Amelia Sacks (Eve Hewson), whose upcoming nuptials to Benji Winbury (Billy Howle) are derailed on the day of her wedding when she discovers the dead body of her maid of honor, Merritt Monaco (Meghann Fahy). As the police investigate Amelia and her fiancé’s family, they discover that each person in the wedding party — from Benji’s imposing mother Greer (Nicole Kidman) to his charismatic best friend, Shooter (Ishaan Khatter) — has been harboring secrets that could destroy the façades they’ve all been working hard to maintain.

The show’s release on Netflix on Sep. 5 marks the culmination of five years of development, and many changes were made to Hilderbrand’s original novel along the way.Hilderbrand told Variety that her “only concern” in the adaptation process was that the Nantucket aesthetic be done properly. “Jenna understood that the aesthetic of Nantucket is understatement. People are not flashy. We drive around in battered Jeep Cherokees with a row of beach stickers on the back. The more beach stickers you have on the back and the crappier your car looks, the more authentically and genuinely Nantucket it is.”

“I really had a blanket theory, or philosophy, that [the novel] was hers to change,” she added. “The storyline, adding characters, taking them away — none of that matters to me. People can go read the book. I watch so much prestige television myself that I just wanted to make sure that Jenna wrote the most compelling television, and she basically had blanket license to do that.”

Lamia said that she’d initially read “The Perfect Couple” as a fan when it first came out. Executive producer Gail Berman emailed her a year later, asking if she’d be interested in adapting it. “[She said] ‘I’ll send it to you if it sounds like something that might be up your alley.’ And I said, ‘Oh no, no. You don’t need to send it. I’ve read it. I’m obsessed with it, and I know how to make it a show. What do I have to do to get this job?’”

In their interview, Lamia and Hilderbrand broke down the biggest differences between the book and the on-screen version of “The Perfect Couple” — including that killer ending.

Amelia’s name in the original novel is actually Celeste

Hilderbrand said that her process for naming characters is a bit nebulous — “They sort of come from the ether” — but that everyone is named with a great deal of intention. Amelia Sacks in the show was originally called Celeste in the novel, though the name was changed for a practical reason: Nicole Kidman played a character named Celeste in 2019 HBO series “Big Little Lies,” and they wanted to avoid confusion.

Featherleigh Dale, meet Isabelle Adjani

In the series, renowned French actor and two-time Oscar nominee Isabelle Adjani plays the wily, seductive Isabel Nallet, a family friend of the Winburys and, perhaps more significantly, paramour of Thomas (Jack Reynor), the eldest son.

Isabel, however, doesn’t exist in the book — though perhaps the model for her personality, however marginally, can be found in the character of one Featherleigh Dale. In Hilderbrand’s novel, Featherleigh is a British interloper whose financial troubles and profligate selfishness cast a significant damper on the weekend’s festivities. Like Isabel, Featherleigh is carrying on an affair with Thomas; unlike Isabel, Featherleigh is somewhat of a basket case, though she plays a crucial role in the way the book reveals who killed Merritt (more on that later).

“The Featherleigh to Isabel name change was also pretty much practical once we knew Isabelle Adjani was coming on board,” Lamia said. “I was a huge fan of hers. I lived in France when ‘La Reine Margot’ came out, which is this iconic film.

“The fact that she was willing to come over to little old Cape Cod and do this role meant that we changed her character from a British society dame to a French one.”

Greer’s lore runs deep

Matriarch Greer Winbury — played impeccably by Nicole Kidman in yet another role as a rich white woman struggling to keep it together — shares many similarities with the book’s Greer. Both versions of the character are murder mystery novelists, though Kidman’s Greer is a successful writer who has somehow convinced her publisher to throw an expensive-looking bash in celebration of her new book (though maybe she paid for it herself?), and Greer in the book is struggling to revitalize her dying series. Both characters find their strength in composure, preferring to remain detached and reserved in their dealings with other people. But the last episode of “The Perfect Couple” portrays a Greer not revealed in the book. In a climactic scene halfway through the finale, Greer unleashes what is perhaps years’ worth of pent-up anger and frustration, revealing to her adult children that she actually met her husband Tag (Liev Schreiber) when she was an escort. On top of that shocking announcement, the man who has been persistently calling her throughout the series — the one that the police say has ties to the Turkish mafia (???) — is, in fact her brother, Broderick Graham (Tommy Flanagan). Greer’s entire backstory as revealed in the series, as well as the existence of Broderick, are not included in the book at all.

Lamia described the process of crafting TV-Greer, and her big revelation, as a “high wire act.”

“We wanted everyone to have a core wound, everyone to have something driving their projected persona,” she said. “Greer is the most concerned with her public image, and with appearing perfect and unsullied. And I knew that I needed her to have something that she was hiding that was dark and dirty, for lack of a better word.”

Amelia’s parents have a much smaller role in the series

Though we get a glimpse of the bride’s relationship with her parents in the series, Celeste’s parents, Karen (Dendrie Taylor) and Bruce (Michael McGrady), are given much more space in the novel. A salesman who’s worked in a department store his whole life, Bruce drunkenly confides in Tag that while he’s never cheated on Karen, he briefly had intense feelings for a former colleague, Robin. Karen overhears and is stunned: though Bruce characterizes Robin as a woman to Tag, she knows that Robin, in fact, is a man. The scene has no real bearing on the murder mystery itself, as it serves mostly to deepen the relational dynamic between Karen and Bruce.

“It was in several, several drafts,” Lamia said. “Many, many, many, many drafts. But there’s only so much room.”

Tag is a stoner

In the series, Tag keeps lighting up. In the book, it’s unclear whether he knows what weed is.

The ending, explained

In the final episode of “The Perfect Couple,” it’s revealed that Thomas’ pregnant wife Abigail (Dakota Fanning) intentionally slips one of Karen’s barbiturate pills into a glass of orange juice, and delivers it to a heartbroken Merritt, who is sitting on the beach. After Merritt drinks the juice, Abigail suggests that the two go into the water, where she holds the maid of honor’s head underwater until she drowns. Abigail’s motive is money: She and Thomas are in debt, and he would have had access to his trust once the youngest son, Will (Sam Nivola), turned 18. Merritt’s affair with Tag, and her subsequent pregnancy, threw a wrench in that plan: if she’d given birth, the clock on Thomas’ trust fund would start over when the baby was born, and they’d have to wait until that kid was 18 until they gained access to the money. Too long, Abigail decided. Hence: murder.

In the book, the drowning is officially ruled an accident by the police, and there’s no direct killer. Greer is the only one who solves the mystery, and she keeps it to herself. Abigail discovers Thomas’ infidelity and drops a pill in Featherleigh’s drink, hoping to put her to sleep so she doesn’t fool around with Abigail’s husband. Featherleigh, however, carries the drink to Merritt instead. Merritt drinks it, and commiserates with the family friend, who then leaves her to go inside. The maid of honor wanders the beach, reminiscing about her affair with Tag, then accidentally cuts her foot on some glass. She wanders into the water to wash it off, spots something shiny at the bottom and realizes it’s the ring that Tag gave her, so she dives in, grows sleepy and drowns.

Lamia said that her goal in adapting the book for television was to “lead to a denouement that would feel utterly fair but also utterly surprising.”

“The best kind of murder mystery leaves you with a feeling that the filmmakers have played fair with you, that you feel satisfied, that maybe you didn’t guess whodunit, but maybe you could have or should have, and maybe if you watch it again you’ll see little clues that were there that maybe you didn’t know were important the first time,” she said.

The novel allows readers to see multiple characters’ perspectives and understand the nuances of their motivations and reasoning, whereas “in a television show you don’t have that luxury,” she explained. “So I wanted a more overt and active motive, and I wanted someone to have meant to kill the person they kill.”

Flash forward

At the very end of the final episode, “The Perfect Couple” flashes forward six months, revealing that Amelia now works at a zoo in London. As she shows some penguins to a couple of children, Greer sidles up to her.

“I’ve written something. Something new,” she says, handing over a manuscript to a new book that she says is about Amelia. The two have a heartfelt conversation in the middle of the penguin enclosure, during which Greer admits that she used to hate Amelia but now doesn’t; in fact, she now hopes that the two of them can be friends. The title of the new book? “Your Move.”

This scene isn’t in the book — which ends with Merritt’s drowning, told from her perspective — and it’s perhaps an attempt at adding a metafictional element to the series: the full-circle serendipity of a murder mystery writer writing about her own real-life murder mystery. Though we’re unsure whether Amelia accepts the olive branch, perhaps the jubilance of the show’s concluding dance sequence — which features the director, Susanne Bier, spinning with the characters — indicates that viewers can come away with a sense of resolution that exists, if not on the shores of Nantucket, at least in the glory of another realm.