Who Killed Merritt? Cast Explained

Warning: This post contains spoilers for “The Perfect Couple”.

Until the final episode of “The Perfect Couple,” the perpetrator behind the death of a maid of honor on the evening before a glamorous wedding on Cape Cod remains unknown.

The six-part Netflix series, based on the novel of the same name by Elin Hilderbrand, begins with the rehearsal dinner for Amelia Sacks (Eve Hewson) and Benji Winbury (Billy Howles).

Everything seems to be fine on the island of Nantucket, but when the body of maid of honor Merritt Monaco (Meghann Fahy) is washed up on the shore of the Winbury villa at the end of the first episode, chaos quickly breaks out in paradise.

The next few episodes show the Winbury family and their loved ones falling apart before and after the planned wedding date. The final episode reveals the results of the police investigation into who killed Merritt.

Ishaan Khatter, who plays Shooter Dival in the series, tells TODAY.com about his reaction when he learned about the ending.

“I for one can say it was a very satisfying ending because I really didn't see it coming,” says Khatter. “And that's all you want as a crime audience – you want to be surprised in a good way. I think in some ways it's the first of its kind.”

Hewson tells TODAY.com she was warned about the killer in advance.

“I think it was Jack Raynor who told me, who got all six episodes and I only got three. I think he sweet-talked (director) Susanne Bier into giving him all the episodes,” Hewson says. “And I just thought, 'But who did it?' And then he told me.”

Fahy laughs and says she can't remember how she found out: “I must have read it in the script.”

Read on to find out the full ending of The Perfect Couple.

Who killed Merritt Monaco?

None of the couples in “The Perfect Couple” are even close to perfect.

Amelia kisses Shooter after her wedding is called off.

Abby Winbury's husband Thomas Winbury cheats on her with a family friend, Isabel Nallet.

And Greer Garrison Winbury's husband is cheating on her with Merritt, who recently told him she was pregnant.

Will, the Winburys' youngest son, overhears the conversation between Merritt and his father Tag, but because of their alibis, both are eventually cleared of any involvement in her death.

The police begin investigating Greer (Nicole Kidman), Benjii's mother, who they believe hired a hitman to kill Merritt after finding out she was pregnant. A questionable loan from Shooter supports the investigators' theory, as do numerous missed calls from suspected hitman Broderick Graham.

The police learn that Broderick is actually just Greer's brother who had to pay off gambling debts. She also confesses to her family that she used to work as an escort, that Broderick was her manager, and that she met Tag at work.

When Amelia finds a pile of photos of Merritt in his drawer, she briefly questions Benji's involvement, but he tells her that Merritt, an aspiring influencer, asked him to paint a photo of her to increase her Instagram followers.

Which leads the detectives to Abby and Thomas.

During Thomas's interview with investigators, he reveals that he had taken some of his grandfather's guns to the beach where Merritt was sitting by the water the night of the rehearsal dinner, but then “changed his mind.”

However, it was Isabel who stopped him from pulling the trigger. Thomas tells investigators he owes Isabel about $2 million, which he planned to repay from his trust fund, which he would have access to when Will, the youngest Winbury, turned 18 in a few months.

However, Merritt's pregnancy would have delayed his access for another 18 years, giving Isabel a motive for the murder.

The police quickly discover that Isabel had an alibi: video footage showed her in the back seat of a taxi with Thomas around the time of the murder.

Which leads them to Abby, who said she slept next to Thomas that night – and who may have a similar motive to Isabel.

Investigators recall a conversation with Gosia, the Winburys' housekeeper, who told them that Abby asked her to wash her clothes, bedsheets and a cup the morning Merritt's body was found.

A flashback explains what happened. Abby, heavily pregnant, takes pills from her husband's nightstand, crushes them and mixes them into a glass of orange juice for Merritt.

The problem is that Thomas had stolen one of Amelia's mother's pills – a barbiturate she was planning to take if her cancer became unbearable – in order to play “prescription roulette”.

Merritt drinks the orange juice and Abby asks her to go swimming, holding Merritt underwater until she dies. The authorities come to arrest Abby at the Winburys' house and she is taken into custody (despite her screaming that she doesn't understand her Miranda rights).

After Abby's arrest, Tag smokes a blunt with Gosia, Will reconnects with the police chief's daughter, Isabel yells at Thomas for telling the police that she was the perpetrator, and Greer looks out to sea alone.

In the final scene of the series, Amelia is now working at London Zoo, seemingly with neither Benji nor Shooter, and Greer stops by to make a special delivery – a copy of her latest book.

Greer asks Amelia to read the manuscript because it is about her. The couple part ways seemingly on good terms, leaving viewers to wonder if they really are the perfect couple?