“The Better Sister” ending explained: Who killed Adam — and why?

Key Points

• Jessica Biel and Elizabeth Banks play estranged sisters swept up in a murder investigation on The Better Sister.

• The whodunnit ends with a number of surprises, from the identity of Adam’s killer to the abrupt death of a supporting player.

• All eight episodes of The Better Sister are currently streaming on Amazon Prime.

This article contains spoilers for The Better Sister series finale, “They’re In Their World.”

Jessica Biel and Elizabeth Banks leadThe Better Sister, a twisty crime thriller about sisters from opposite sides of the tracks — and the dead man that brings them back together.

That dead man is Adam (Corey Stoll). Stay with us here: Adam, a successful Manhattan attorney, is married to Chloe (Biel), a magazine executive. First, however, he was married to Chloe’s sister, Nicky (Banks), now estranged after struggling with addiction issues. Adam and Nicky have a child, Ethan (Maxwell Acee Donovan), though Nicky no longer has custody for reasons we’ll get into below.

It’s Adam’s mysterious death that reunites the sisters, plunging them into a dizzying story that extends well beyond its whodunnit premise.

The Better Sister, which is currently streaming in full on Amazon Prime Video, was adapted by co-showrunners Olivia Milch (Ocean’s 8) and Regina Corrado (Mayor of Kingstown) from Alafair Burke’s 2019 novel of the same name.

“[It’s] very Shakespearean for two women to be with the same bad man, to have the son who lives in the father’s shadow and can’t get out from under it, and the women who seek revenge,” Banks previously told Entertainment Weekly of what attracted her to the series. “These are big, fun vibes that are in all the great stories, right? They are Lady Macbeth-ing this entire scenario.”

So, how do they “Lady MacBeth” the scenario? How does The Better Sister end? Who really killed Adam — and why? Read on as we answer these questions and more with our The Better Sister ending explainer.

What is The Better Sister about?

The Better Sister is about a pair of sisters navigating the aftermath of Adam’s murder. Ethan, Nicky and Adam’s son, is arrested for the murder after his DNA is found at the scene. Later, it’s discovered that Ethan harbored a great deal of hate for his father. This brings the two sisters, both estranged and living very different lives, back together.

Tensions are high primarily due to the reason Nicky is no longer Ethan’s guardian. When Ethan was a baby, he was found floating in a pool next to a drunk and intoxicated Nicky. This led to Adam and Nicky’s divorce, as well as her move to Ohio, where, despite the divorce, she continues to help care for Debbie (Deirdre O’Connell), Adam’s ailing, foul-mouthed mother.

The Better Sister is rounded out by a plot involving a pair of detectives, Guidry (Kim Dickens) and Bowen (Bobby Naderi), investigating Adam’s murder.

Their investigation intersects with the various allegations of fraud, human trafficking, and manslaughter swirling around Gentry Group, the evil corporation for which Adam worked. As we learn, Adam was speaking with the FBI about the dirty deeds of Gentry and its overlord, Bill Braddock (Matthew Modine). They wonder if his murder was an attempt by Gentry goons to silence them.

Throughout the season, as Chloe and Nicky withstand Ethan’s punishing trial, the pair reconnect over their shared trauma of living with Adam, who was physically and emotionally abusive.

Who killed Adam on The Better Sister?

Adam wasn’t killed by Ethan or Gentry goons, but rather Nicky.

The final episode begins with a flashback showing how Ethan called Nicky the day before his death, tearily telling her he saw Adam physically assault Chloe. This prompts Nicky to drive to the Hamptons and demand custody of Ethan.

He calls her an addict, and she reminds him of something we only just learned: Her pool blackout was caused by Adam, who had secretly drugged her in order to squeeze her out of he and Ethan’s lives.

Nicky threatens Adam, who begins choking her. She stabs him in the neck with a small pocket knife to defend herself, then leaves the scene of the crime.

But that’s not the end. Later in the episode, Ethan reveals that he stumbled upon Adam while he was bleeding out on the floor, still alive. Assuming Chloe killed him, Ethan thought to help cover for her by making it look as if his murder was motivated by an attempted robbery. (This is how his DNA ended up all over the scene.)

Ethan admits to Nicky that he allowed Adam to die, choosing not to call an ambulance. While he feels some guilt, especially since he was acquitted due to a lack of evidence, he doesn’t regret it. “When I think about it now, I’m glad I didn’t. I would do it again, to protect her,” he admits.

Nicky reveals to Chloe that she killed Adam. Chloe, who’d grown to hate Adam as much as Nicky, comes to see it as Nicky intended: an act of protection.

What happens at the end of The Better Sister?

The Better Sister ends with Chloe working to pin Adam’s murder on Bill Braddock, his boss at the Gentry Group. Nicky, too, covers her tracks by using dirty tricks to dig up dark secrets from Guidry’s past, thus compromising the detective’s investigation. A good thing, too, as Guidry had more or less figured out Nicky’s involvement in the murder.

Chloe’s plan intersects with the FBI’s interest in Adam and the Gentry Group. She learns via Jake (Gabriel Sloyer), her secret lover and Adam’s colleague at Gentry, that Adam had records detailing all of Gentry’s crimes to potentially hand over to the FBI.

Chloe finds the documents (and an audio tape that directly implicates Bill), but then hands them over to Bill. She says she wants nothing to do with the FBI or the investigation, saying she’s scared all the time. “Whatever Adam knew, he died for,” she says. Telling Bill that she just wants to focus on putting her family back together again, she says, “Consider my allegiance pledged from here on out.”

But it was just a ruse. Previously, she made copies of Adam’s files and passed them along to Bowen. While in the office, she plants the pocket knife in Bill’s office. After investigating Bill’s office (and finding the knife), Bowen arrests Bill to great fanfare from the press.

This infuriates Guidry. She had uncovered ample evidence linking Nicky to Adam’s murder, including intel gleaned from Adam’s mother about how Nicky knew details about Adam’s murder that only the murderer and detectives would know. Furthermore, she surreptitiously obtained DNA samples from Nicky that she believed would help place Nicky at the scene of the crime.

But Nicky, knowing Guidry would be a problem, hired a PI to dig up dirt about Guidry’s past mistakes in law enforcement, which she then leaked to the press. The controversy gets Guidry removed from the investigation and put on leave.

“Good for you, getting it all wrong,” Guidry mutters while watching Bill’s arrest on TV at a bar. “Idiot.”

The series ends with Chloe and Nicky on a beach, relishing their rejuvenated relationship and their upcoming collaboration on a tell-all book about Adam’s murder.

But we’re not done just yet…

Who killed Jake?

The Better Sister ends with a surprise. After the scene with the sisters on the beach, we’re shown another dead body. It’s Jake, Adam’s former colleague and Chloe’s lover. Who killed Jake? If you’d like that answer, you better tell Amazon you want a second season of The Better Sister.

Speaking with EW, Milch and Corrado said they hope the question who killed Jake “can be answered at some point” in the future.

“We have some ideas and thoughts,” Milch told us. “And we have an answer. But I think that, when it comes to these sisters, there’s always some mystery to uncover.”

Related: The 19 best thriller movies on Amazon Prime Video to get your pulse up

Like Adam, Jake was also talking to the FBI. He was paranoid about a rogue agent, Edward Olivero (Frank Pando), who was blackmailing him. But he could also have run afoul of Gentry, where he was deeply embedded, or faced the wrath of Nicky and Chloe. Basically, he was a loose end for a lot of potential suspects.

Where can I watch The Better Sister?

All eight episodes of The Better Sister are now streaming on Amazon Prime.

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