The surprising reason Netflix changed the ending in The Perfect Couple.

The Perfect Couple on Netflix is the latest murder mystery everyone is talking about.

If you've recently started watching, or you binge-watched the whole thing in one sitting like me, you've likely been captivated by the wealthy and incredible weird Winbury family.

The show is based on Elin Hildebrand's novel of the same name, with the author joining forces with showrunner Jenna Lamia to transform the story for the screen. In more ways than one.

"People can go buy the book. Anybody can buy the book and read it — that's an experience. I watched so much prestige TV and I know what's good, and I know that directly translating the novels to the screen may not be the best way to do it," Hildebrand told Town & Country Magazine.

From changes to key plot points (including the murder) and additional cast details, here are all the biggest differences you might have missed between The Perfect Couple book and Netflix show. And you know, this article includes spoilers. Duh.

Merritt (Meghann Fahy) is the victim of a senseless murder in The Perfect Couple. Image: Netflix.

Who killed Merritt in The Perfect Couple?

On the morning of her best friend Amelia's (Eve Hewson) wedding ceremony, maid of honor Merritt (Meghann Fahy) is found dead, washed up on the shores of the Winbury residence. Merritt had been having an affair with Greer's (Nicole Kidman) husband, Tag (Liev Schreiber).

Amelia is inconsolable, and pulls further away from her fiancé Benji (Billy Howle).

The mystery of Merritt's death is the key focus of the series, as the family falls to pieces around the case and Abby and Benji delay their nuptials.

In both the book and the film, Merritt is killed by Abby (Dakota Fanning).

However, the motive behind the murder is vastly different. In fact, the book is actually far more tragic in my opinion.

Dakota Fanning is perfection as Abby. Image: Netflix.

Why does Abby kill Merritt in The Perfect Couple?

In the book, Merritt's death is accidental. But director and executive producer Susanne Bier told Netflix she likely "wouldn't have done the series had it not been intentional."

The novel reveals that Abby is aware that her husband Thomas (Jack Reynor) is having an affair with a family friend (called Featherleigh in the book, but Isabel in the show). Abby slips a pill into the water of her husband's mistress, hoping she'll drink it and pass out so they don't sleep together.

Merritt accidentally ends up drinking the water, a fact Abby is not aware of. Shortly after, Merritt wades into the water and loses her balance. She falls under and drowns, as she succumbs to the effects of the drug. But that's not all.

The book ends with Greer piecing the puzzle together, after the police rule Merritt's death an accident.

"Abby may not even realize she's to blame, and Thomas will never put two and two together," the book reads. "The secret resides with Greer, and with Greer it will remain until her death."

Yep! Abby has no idea she's to blame. Which, in my opinion, makes the ending of the book a whole lot sadder as Merritt's death is left a mystery and the culprits aren't even aware of what's taken place.

The Netflix show chose a more sinister route, and honestly I'm all for the total tone change of making Abby a psychotic murderer.

In the series, Abby intentionally drugged and murdered Merritt in order to secure her husband's inheritance for her unborn child. Why? If Merritt had given birth to Tag's child, Abby would've had to wait 18 more years to receive the money. And girlie pop wanted that money, enough to kill for it.

The change transformed the show into a clear cut murder mystery, which may have translated better on-screen. It also gave lovers of the book quite a shock, adding another layer for fans to enjoy.

Greer's backstory was created for the show. Image: Netflix.

The introduction of Will Winbury.

Because of the changes to the plot, the TV show also needed a new character: enter little brother Will Winbury.

Played by Sam Nivola, Will is a sweet and naïve addition to a family of — let's be honest — numb and cold-hearted folks. His sweetness offsets their sharpness, and allows for the introduction of the inheritance plot point.

Karen's pills and Merritt's death.

In The Perfect Couple book, Karen's pills are mentioned throughout as she makes her end of life plans. But she's not involved in Merritt's death.

In the book, Abby "sneaks downstairs, steals one of Greer's extra-strong sleeping pills, and slips it into the water glass meant for Featherleigh."

Was Greer's backstory different in the book?

In the show, Greer's slow unravelling from the picture perfect housewife is a major plot point.

We gradually see her transforming and, in a moment of anger after being held for questioning by detectives all night long, Greer unleashes on her family as she reveals the true nature of her past.

She was an escort, who was hired by Tag at least four times before they began dating. The big reveal came after Tag threatened to spill her secrets in a menacing and public way. The change to her backstory allowed Greer to have a huge "f**k you" moment to her cheating and useless husband.

"I'm not living like this. I'm not living in fear of exposure anymore: Do you hear me? I'm not living with your goddamn mess, I'm not cleaning everything up for you," she yells in the final episode. "I'm done with your ego, I'm done with your bullshit. I am done, do you hear me? Done. I'm not taking care of everything everyone anymore. I'm done! I'm done with living the lie."

None of this is included in the books, and was actually thought up by Nicole Kidman herself.

Eve Hewson stars as Amelia. Image: Netflix.

Amelia and Shooter's kiss.

In the show, Amelia has a secret, long-held crush on Benji's best friend Shooter (Ishaan Khattar). It's definitely reciprocated, as Shooter pines for Amelia.

On screen, they share a brief kiss after her wedding has been cancelled due to the murder. But in the book, they were actually going to elope on her wedding day.

The changes made Amelia's emotional journey on the show more complex, and allowed her to end her journey with a move to London to "discover" herself.

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