“The Perfect Couple” Ending Explained: All About the Series' Major Twist — and How It Differs From the Novel

The unlikely killer’s identity is exposed in the season finale of Netflix’s murder mystery 'The Perfect Couple'

Warning: The Perfect Couple spoilers ahead!

Netflix’s The Perfect Couple is a perfect whodunnit that keeps viewers guessing until the very end.

The six-episode miniseries, based on Elin Hilderbrand’s New York Times bestselling novel by the same name, opens as Amelia Sacks (Eve Hewson) is about to marry Benji Winbury (Billy Howle), a member of one of the wealthiest families on Nantucket, Mass. But their lavish wedding plans are derailed when Merritt Monaco (Meghann Fahy), Amelia’s best friend and maid of honor, is found dead on the shore of the Winbury estate, Summerland — just hours before Amelia and Benji were to say “I do.”

Suddenly, everyone in the Winbury family is a suspect in Merritt’s murder. As Detectives Dan Carter (Michael Beach) and Nikki Henry (Donna Lynn Champlin) work to determine who drowned the social media influencer and why, the investigation zeroes in on Tag Winbury (Liev Schreiber) — Benji’s father who was having an affair with Merritt and got her pregnant — and Greer Garrison Winbury (Nicole Kidman), the family matriarch and famed murder-mystery novelist.

Tag is eventually eliminated as a suspect thanks to his smartwatch data, which reveals he was sleeping at the time of Merritt’s murder. But Greer, who is well aware of her husband’s indiscretions and future love child, remains a prime suspect — and Detectives Carter and Henry believe they’ve discovered the damning evidence to prove their case in the season finale.

Related: Where Was The Perfect Couple Filmed? All About the Real-Life Locations Behind the Netflix Show

But The Perfect Couple finale takes more twists and turns before revealing Merritt’s murderer and their motive. Keep reading for The Perfect Couple’s ending, explained — from the killer’s identity to how the finale strayed from Hilderbrand’s book.

What happens in The Perfect Couple finale?

At the beginning of the season finale, Detectives Henry and Carter believe they have nailed down Merritt’s murderer — and it’s the Winbury family matriarch, Greer. The cops’ working theory is that Greer hired Broderick Graham, a known criminal with ties to the Turkish mafia, to kill her husband’s pregnant mistress. Their proof? A $300,000 wire transfer from family friend Shooter Dival to Broderick, which Carter and Henry surmise Greer requested because of Shooter’s diplomatic immunity.

That theory is busted, however, when Greer explains that Broderick is actually her brother and the $300,000 wire transfer was a loan to pay off his gambling debts. The revelations continue when the brother-sister duo return home to Summerland, where the family is currently meeting with Greer’s PR team to deal with Tag’s public meltdown at her book party. Greer introduces her secret brother to the rest of the Winburys — and reveals that she and Tag first met when she was working as an escort, and he was a paying customer.

Winbury family drama aside, Carter and Henry are still working to solve Merritt’s murder. After Amelia mentions to her parents that Merritt was found with barbiturates in her system at the time of her death, her cancer-stricken mother, Karen, discovers that one of her three pentobarbital pills (which she obtained for euthanasia purposes) is missing. Now, all fingers point to the eldest Winbury son, Thomas (Jack Reynor), who is known for stealing pills to play “prescription roulette.”

While Tom admits to stealing Karen’s pill, he insists to the police that he did not give it to Merritt. Instead, he proposes a different theory: That his mistress, family friend Isabel (Isabelle Adjani), poisoned Merritt. He explains that he owes Isabel $2.5 million and he planned to repay her when he gained access to his trust fund, which occurs when the youngest Winbury child turns 18. Their youngest brother, Will (Sam Nivola), was due to turn 18 at the end of the summer — but with Merritt pregnant, the clock on the trust would reset another 18 years.

Isabel may have had motive and opportunity — she is one of the last people seen with Merritt — but she also had an alibi. Video footage from a cab driver shows her leaving Summerland with Tom to hook up at her hotel, eliminating her as a potential suspect.

Who killed Merritt in The Perfect Couple?

Tom may have wrongfully accused Isabel of murdering Merritt, but his interview with Detectives Carter and Henry does indirectly lead them to the killer. The person responsible for killing Merritt is Tom’s pregnant wife, Abby Winbury (played by Dakota Fanning).

After questioning Tom, Carter and Henry realize that Abby has been lying to them all along about Tom’s whereabouts the night of the murder. (She claimed he woke her up when he got into bed that night, but the taxi footage proved otherwise.) Detective Henry also recalls Abby frantically washing a glass the morning after the murder and acting nervous when questioned. Though the cops won’t be able to test the glass for traces of pentobarbital, they can connect the traces of tallow found in Merritt’s hair to the skincare products Abby uses. With the evidence in hand, the detectives show up to Summerland to arrest Abby for Merritt’s murder.

“I can’t go to jail, I’m pregnant,” she insists, as she is placed in handcuffs — while the rest of the Winbury family hangs by the pool.

After Abby is taken away by police, a flashback scene reveals what really happened the night before the wedding. Abby, after watching Tom leave drunkenly with Isabel, crushes up the pentobarbital pill into a glass of fresh-pressed orange juice. She delivers it to a visibly upset Merritt and commiserates with her about how disappointing and undependable men can be.

“You really can’t trust them to just get the job done,” Abby says sinisterly before convincing Merritt to join her for a late-night swim.

Then, as a visibly woozy Merritt stumbles in the water, Abby forces her head below the surface until she drowns. Once she’s dead, Abby calmly returns to the house — leaving Merritt’s lifeless body floating in the ocean.

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Why did Abby kill Merritt?

Just as Tom suggested that Isabel killed Merritt over the trust fund money, Abby’s motive for murder is financially fueled. For Abby, nothing will threaten the luxury lifestyle she has grown accustomed to as a Winbury — particularly not Tom’s debts or his infidelity. She pressures Tom into asking Tag for a loan so that they can get a new apartment (in the Beresford, an iconic New York City building along Central Park), and knows that they are only weeks away from Tom accessing his Winbury inheritance.

But when the hiccup of Merritt’s pregnancy reveals itself (and carries the potential to delay their influx of cash by 18 more years), Tom attempts to “make that situation just go away” by scaring her with his grandfather’s gun into getting an abortion. But he chickens out and instead leaves drunkenly with Isabel — which Abby witnesses from her balcony.

Abby then takes matters into her own hands to get rid of the threat to their inheritance money. “If you want something done right, you have to do it yourself,” she tells Merritt on the beach before killing her.

How does the ending differ from the book?

There are some key differences between the ending of the Netflix series and Hilderband’s novel. While Abby is responsible for Merritt’s death in both versions of The Perfect Couple, in the book, it is accidental as opposed to murder.

In the novel, Abby slips a pill into the drink of Tom’s mistress (named Featherleigh, not Isabel) — with the hopes that it will put her to sleep and prevent her from fooling around with Tom for the night. But Merritt accidentally consumes the drink instead of Featherleigh, and then cuts her foot while wandering the beach late at night. Merritt enters the water alone to wash off her foot, and is distracted by something shiny at the bottom of the water. She dives for it, realizing it is a ring that Tag gave her, but becomes sleepy from the pill and drowns.

Merritt’s death is ruled an accident by the police in the novel, and only Greer discovers the truth of what happened. But the decision to change Merritt’s death from an accidental drowning to an intentional murder came from The Perfect Couple’s showrunner Jenna Lamia and producers Gail Berman and Hend Baghdady, according to Tudum.

“[We] all agreed right then and there [that] there needed to be a murderer, and there needed to be a motive for that murder,” Lamia told the outlet.

Where do Amelia and Benji stand?

Throughout The Perfect Couple, Amelia and Benji’s relationship is a roller coaster. In the first episode, Benji delivers a tearful toast to his bride-to-be, declaring her his penguin (as penguins mate for life). But by episode 4, their union is on the rocks after Benji discovers Amelia and Shooter — his best man — kissing.

The couple briefly reconcile in the penultimate episode, with a drunken Benji and Amelia hooking up in the kitchen at Greer’s disastrous book party. But in the season finale, Benji bids farewell to Amelia after Abby’s arrest, sending her off in a taxi while he stays behind.

“I really wanted to label you ‘woman who lied to me,’ but the truth is, you are so many good things too,” Benji tells Amelia in one of their final conversations. “You’re ‘woman who inspired me,’ ‘woman who made me laugh so much I choked on my beer,’ ‘woman who I really, truly f------ loved.’ ”

Where do Tag and Greer stand?

Tag and Greer, the so-called perfect couple who inspired all of Greer’s novels, also call it quits in the season finale. Following Abby’s arrest, Greer tells Tag that he can remain at the Nantucket house, while she goes to New York to write her latest novel.

“It never occurred to me, not even once, that you might actually leave me,” Tag tells his wife — despite all of his indiscretions during their marriage.

How does The Perfect Couple end?

The final scene of The Perfect Couple flashes forward six months and shifts from Nantucket to London.

There, Greer tracks down Amelia, who is working at the London Zoo (in the penguin exhibit). Greer reveals that she has finished her latest novel and, rather than writing about her experience as an escort, she has written about Amelia. Despite their previously strained relationship, Greer tells Amelia she hopes she will read it and call her once she has.

The dedication on the book, which is titled Your Move, reads, “To Absent Friends, and hopefully, to new ones” — referencing Amelia’s loss of her best friend, Merritt, and the prospect of a friendship between Amelia and Greer. Lamia, The Perfect Couple’s showrunner, revealed that the shift in Greer’s writing illustrates what the show — and the novel — are really about: female friendships.

“That’s the truest love story of the whole show,” Lamia told Tudum, referencing Amelia and Merritt.

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