The Undoing finale: what happened in episode 6, who is the killer - and where to watch the series starring Nicole Kidman

While our social lives have been put on pause during the pandemic, we’ve been relying on binge-watching TV series for nightly entertainment.

Yet HBO and Sky Atlantic only released one episode per week of the networks’ newest drama, The Undoing.

Instead of the week-long wait putting viewers off, people have become addicted to the show, eagerly looking forward to Monday nights when the new episodes were released.

The last episode in the six-part mini-series, which stars Nicole Kidman and Hugh Grant, dropped on 30 November, and fans have been going wild after Elena’s killer was finally revealed.

Here’s everything that happened in the last episode, and how you can stream the series.

Be warned, there’s plenty of spoilers ahead.

What were The Undoing fan theories?

The Undoing’s dramatic plotline follows rich Manhattan couple Grace (Nicole Kidman), a clinical psychologist, and Jonathan Fraser (Hugh Grant), a children’s cancer doctor, and their teen son, whose seemingly perfect lives unravel when Jonathan is arrested for the murder of his secret lover, Elena.

Each episode teased viewers with an insight into who might have committed the heinous crime, as Jonathan maintained his innocence throughout - despite spending the night with Elena just moments before she met her gory death.

Some fans suspected Grace herself to have killed Elena, due to her weird fascination with the young mother and her tendency for late-night walks. Perhaps she had discovered Jonathan and Elena together and was overcome by a jealous rage?

Another theory focused on the couple’s young son, Henry (Noah Jupe), who was aware of the affair and perhaps killed Elena in an attempt to save his parents’ marriage.

Viewers even thought it could have been Grace’s filthy rich father, Franklin (Donald Sutherland) who hated his son-in-law and could have sought to separate Grace from her husband by framing him for murder.

Of course, there was also Elena’s own husband, who had to be a suspect because, as Grace’s best friend Slyvia (Lily Rabe) said at the beginning of the series, “It’s always the husband”.

There were so many theories that viewers somehow managed to forget about Jonathan, the prime suspect himself.

Many incidences throughout the series pointed to Jonathan’s guilt - the fact that he fled New York after Elena’s death, he had been lying about being fired from his job, he had visited the dry cleaner after discovering Elena’s body, and his own wife, a clinical psychologist, had diagnosed him with narcissistic personality disorder.

What happened in the last episode of The Undoing?

In the previous episode, we found out that Jonathan had not in fact killed his family dog when he was a teenager, by accidentally letting it run out of the house and into oncoming traffic.

He’d managed to keep it secret from his wife and son that it was his four-year-old sister that had died, and he had since been estranged from his family.

In a video call with Grace, his mother had said Jonathan had felt “no remorse” and shown no signs of sadness after the incident.

Then, the episode ended with Grace finding the weapon that had been used to kill Elena - a sculpture hammer - in Henry’s violin case.

In the finale episode, we found out that Henry had discovered the hammer at the family’s beach house, hidden in the fire pit.

When confronted with this information, Jonathan denied having put the weapon there, instead pointing his finger to Elena’s husband.

Along with the family lawyer, Haley Fitzgerald (Noma Dumezweni), it was decided that the weapon - which Henry had cleansed of all DNA by running it through the dishwasher - would not be handed to the police.

Instead, as the ongoing trial seemed to be progressing within Jonathan’s favour, Grace decided to take the stand to testify that her husband could not have committed the callous crime.

Yet, the morning before she was to bear witness, Grace met up with Slyvia, who had connections with the prosecuting lawyer, but viewers didn’t get to see what was said between the two.

When Grace took the stand, she seemed to paint a good case for Jonathan - she said he was empathetic, he was a good father and he wasn’t capable of committing what he had been accused of.

However, when the prosecuting lawyer questioned her, things took a turn and Grace began to unravel.

The lawyer somehow knew about the incident with Jonathan and his sister, and what his own mother had said about him, and it was clear she’d been fed that information from Slyvia, who Grace must have asked to change the direction of the trial.

Viewers inferred that, after speaking to Jonathan’s mother and the subsequent finding of the murder weapon, Grace had changed her mind about her husband’s innocence and wanted to see him jailed for his crime.

At this point, we still weren’t sure who had done it, but things were beginning to look sticky for Jonathan and all the evidence was pointing to his guilt.

Who was the killer in The Undoing?

After Grace’s witness statement, Jonathan was filled with rage once he realised how his own wife had turned against him.

The morning of the last day of the trial, he decided to “take Henry for breakfast” but instead he drives his son out of New York, and Grace is alerted by the school that Henry is not in attendance.

While the police scrambled to track the car down, viewers were finally confronted with Jonathan’s inner thoughts of what happened on the fateful night.

We saw Jonathan go over to Elena’s studio, where the lovers had an argument, with Elena telling Jonathan he would “never get rid” of her and that she’d always be in his life.

In a fit of rage, presumably caused by the threat of his affair being exposed, Jonathan attacked the young mother.

She chased after him with her sculpting hammer, which he ultimately used to commit the very crime he had been charged with.

The scene flashed back to Jonathan driving Henry out of the city, and he finally confessed what he had done to his son, who proceeded to become very scared.

By this point, the police, along with Grace’s father’s helicopter, had caught up with the runaway vehicle, and in a desperate last attempt to salvage his reputation - or so he thought - Jonathan stood on the edge of a bridge like he was going to jump.

Grace managed to catch up with the pair, taking a terrified Henry away from his father, who had really shown his true colours.

The episode ended with Jonathan being arrested, and Grace, her father and Henry flying back to New York in the helicopter, with Grace looking incredibly relieved and seemingly happy with her decision to finally believe her husband was guilty.

Some viewers were happy with the ending, shocked by how Jonathan had duped his family into believing his innocence, whereas others felt they had been robbed from a dramatic plot twist.

How can I stream The Undoing?

If you missed the last episode of The Undoing, or fancy watching the series again, it is available to stream on Sky catch up or Now TV.