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The Ending Of The Undoing Season 1 Explained

HBO's latest high society murder mystery has finally finished coming undone. What started as a tense exploration of the social hierarchy at an expensive private school in Manhattan quickly turned into a juicy whodunit that shined a spotlight of potential guilt on just about every character. But despite the War and Peace-sized list of suspects, by the time the credits rolled on the finale of The Undoing, we learned exactly who actually killed Elena Alves (Matilda De Angelis).

At the center of it all is Grace Fraser (Nicole Kidman), a psychotherapist whose husband, Jonathan (Hugh Grant), has been the prime suspect in Elena's murder since it was revealed that he'd been secretly having an affair with the woman. Throughout the season, Grace has worked hard to keep her family together, even when it has meant accepting that her husband has been keeping a litany of painful secrets from her. She has been one step behind almost every turn the case has taken. However, in the final episode, she takes matters into her own hands and sets into motion events that eventually unmask the true killer. 

Here's everything that went down in the finale of The Undoing season 1.

A shocking discovery puts Henry in the spotlight

The penultimate episode of the series ended with the shocking discovery that Grace and Jonathan's son, Henry (Noah Jupe), was in possession of the sculpting hammer that was used to kill Elena. The murder weapon has been missing until now, and its discovery raises the question of whether Henry was possibly involved in the grisly death.

This is a serious shock to Grace, who has spent much of the season trying to mitigate the stress the entire nightmare has been causing her son. When pressed to explain himself, Henry says that he found the hammer at the family beach house and hid it to try and protect his father. His dad pays him back for his mafia-like loyalty to the family by... promptly trying to throw him under the bus.

When Jonathan suggests the possibility that Henry could be responsible for the murder, Grace is disgusted. Although Grace has clearly had a hard time knowing which way is up during the murder investigation, Jonathan trying to shift the blame to their own son seems to clarify things for her. When her father, Franklin (Donald Sutherland), pulls her aside and urges her to see what is really going on with Jonathan, Grace responds, "I do see. I'll fix things."

Grace makes her move

While she continues to cooperate with Jonathan's legal team, Grace begins working behind the scenes to make sure the truth comes to light. She calls up her friend, Sylvia (American Horror Story star Lily Rabe), and asks for a favor. Although the audience doesn't get the particulars of what the two women discuss when they go on an early-morning walk around Central Park, we later see Sylvia chatting with her old friend, Catherine Stamper (Sofie Gråbøl) — a.k.a. the attorney prosecuting Jonathan's case — in the bathroom.

As their list of witnesses begins to run dry, Jonathan's lawyer, Haley Fitzgerald (Noma Dumezweni), thinks that they've diffused enough of the suspicion against him that they can rest the case and put it in the hands of the jury. But Grace suggests that she should take the stand and give her husband one last vote of confidence. Fitzgerald is rightly concerned about this. "But what is your truth?" she asks Grace. "I'm having a little trouble tracking it."

Grace assures Fitzgerald and Jonathan that she is prepared to unequivocally testify that she believes in Jonathan's innocence. However, her true desire to be called as a witness has nothing to do with securing a non-guilty verdict for her husband.

A cross-examination destroys Jonathan's legal defense

Back in court, Grace takes the stand, where she uses her relationship as Jonathan's wife and her expertise as a psychotherapist to assure the jury that he is an empathetic man who she doesn't believe to be capable of violence. However, that all crumbles once Stamper steps up to cross-examine. Against the objections of Fitzgerald, Stamper uses a series of very personal details to poke holes in the testimony Grace just gave. She plays the 911 call Grace made when Jonathan first reappeared after being on the run to show that Grace was, at one point, very afraid of her husband's capacity for violence.

Then she asks Grace about Jonathan's family. Grace shares the story of Jonathan's younger sister and the way that his own family was disturbed by his lack of grief after her death. This casts serious doubt over her claim that he is an empathetic person. Furthermore, Stamper brings up the fact that Grace once told Sylvia that she believed Jonathan suffers from narcissistic personality disorder. While Grace says that it's not a professional diagnosis, she does admit, "I know who and what I married."

The admissions are a shock to everyone, especially Fitzgerald and Jonathan. Little did they know that Grace had worked behind the scenes to have Sylvia feed information to Stamper to ensure that she would know exactly what questions to ask during the cross-examination. In light of her testimony, it now seems that a guilty verdict for Jonathan is certain.

The nail-biting finale

After confirming what seemed obvious since the first episode, the series finally gives us the unfiltered truth of what happened to Elena a series of flashbacks. We see Jonathan visiting her art studio on the night of the fundraiser, where the two hook up. Afterward, Elena expresses an interest in getting to know Grace and Henry better. Jonathan warns her not to get close to his wife and son, otherwise he'll hurt her — a threat that she doesn't take seriously. He responds by brutally assaulting her, which causes Elena to come at him with her sculptor's hammer. He takes it from her and knocks her down. But instead of walking away, he kills her in a horrific display of psychotic violence.

In the present, Jonathan asks his son to join him for breakfast one last time. However, the breakfast turns into an Amber alert when Jonathan drives out of the city and toward Canada with Henry in tow. The police catch up to them and Grace makes a dramatic entrance on Franklin's private helicopter to rescue her son while Jonathan is apprehended by the police.

The Undoing was a winding road that eventually came right back to where it began. The image Jonathan created as a selfless pediatric oncologist and all-around good guy was a skillful fabrication that fooled many around him, including his own wife. But by the end, the seams and the cracks had begun to show, and everyone realized the most likely suspect in the case of Elena's murder proved to be the guilty one.