It’s the thriller that’s gripped the nation throughout a second lockdown and reminded us all what it’s like to have to wait for a new episode to drop every week.

The latest viewing figures show that The Undoing’s launch audience was bigger than Game Of Thrones, and is set to become the biggest US series to ever launch on Sky Atlantic.

Based on the 2014 novel You Should Have Known, the drama is written by Big Little Lies creator David E Kelly and directed by The Night Manager’s Susanne Bier.

Now, as we approach its finale, we take a look at the characters in the frame for the brutal murder of Elena Alves.

Warning: Spoilers up to and including the penultimate episode.

Grace Fraser

Played by Nicole Kidman, Grace is a psychotherapist living a seemingly charmed life in her beautiful Manhattan apartment, with her doctor husband Jonathan and loving young son Henry.

But her reality falls apart after when a new mum at her Henry’s elite private school is murdered and Jonathan subsequently goes missing.

Grace seems blindsided by his disappearance and appears equally shocked when detectives tell her that her husband had been dismissed from his job after disciplinary action over “inappropriate contact with a patient’s relative”.

That person was Elena Alves.

Grace had previously met Elena at a committee meeting, and later ran into her in the gym changing rooms where a naked Elena got a little too close for comfort.

The pair also shared a swift kiss in the lift on the night of Elena’s murder. After her death, we see that Elena had painted a detailed portrait of Grace, which was found in her studio.

While we know Grace alerted the police the moment her husband came out of hiding and revealed himself to her on the veranda, we also see her standing by him – and holding his hand – as he attends his trial.

CCTV footage located by police showing Grace walking the streets just a block from Elena’s studio – where she was found bludgeoned to death with her own sculpting hammer – is yet to be explained.

Grace says she was just going for a walk but can’t actually remember being there. Could her motive have been more sinister?

As the drama’s lead protagonist, we see everything from Grace’s perspective, but is she as reliable a narrator as we think?

Jonathan Fraser

Portrayed by Hugh Grant, Jonathan is a paediatric oncologist who treats children with cancer.

While he admits he did visit Alves on night of her death – and more to the point that they argued before they had sex – he says she was fit and well when he left her.

He says it was when he came back to the studio after going to a bar that he found her dead, and then in panic fled, leaving bloody footprints behind him and his DNA all over the crime scene.

We know he’s highly sexed, unfaithful, and a bit of a narcissist. He is also the father of Elena’s baby girl now being cared for by her husband Fernando.

And it’s not the first time he’s strayed. Jonathan tells his lawyer he’s been unfaithful to Grace at least once before.

But his admission during a TV interview that he “loved” Elena would suggest that the relationship was rather more than a fling.

Hardly the model dad, we discover Henry saw him getting close to Elena outside his school, and while Jonathan saw him, he didn’t do anything to put his son’s mind at rest.

We also know his lacklustre babysitting skills led to the death of his four-year-old sister Katie when he was a teenager.

Jonathan is estranged from his family, and his mother tells Grace he never showed signs of guilt or remorse after his sister’s death. It’s never a good sign if your own mum outs you as a sociopath.

Meanwhile, Jonathan totally denies killing Elena. He regularly tells Grace it was in fact Elena who was “stalking” him, and that she was “obsessed”.

But if he was the culprit, he would say that, wouldn’t he?

Fernando Alves

A cuckolded husband, played by Ismael Cruz Cordova, Fernando is literally left holding the baby after Elena’s death.

He knew about his wife’s infidelity, and also knew that his daughter was not his own.

Quietly spoken and unassuming, the defence manage to rile him to anger in court, after repeatedly suggesting he is a key suspect who the police failed to investigate properly.

We know that he and Elena had been having marital difficulties. And he was the second person on the scene, after his son Miguel discovered the body.

But Fernando also has an alibi – his son – as well as CCTV evidence backing up his claim that he didn’t leave his building on the night of the murder.

We see him let Jonathan into his flat, allow him to hold the baby, and appear surprisingly polite and welcoming – all things considered.

On the flip side, he has been following Grace late at night. And calling her on the phone. Is he keeping an eye on her, or is he a darker figure than he seems?

If it was a crime of passion, the husband is always the first suspect, right?

Franklin Reinhardt

Acting legend Donald Sutherland plays Grace’s rich and influential father Franklin, who pays Jonathan’s $2m (£1.5m) bail fee as well as stumping up for his expensive defence lawyer.

He’s very protective of Grace and he’s never liked Jonathan. In fact, he thinks he’s guilty and has even threatened to kill him if he ever harms his daughter or grandson.

We also know he was regularly unfaithful to his wife, Grace’s mum.

While we know he lent Jonathan money before the murder, we understand he thought it was for Henry’s school fees.

He goes along to court to support Grace, and considers all the TV coverage of the trial to be just “entertainment”

But then there was the moment his character showed himself in a whole new light – his “c***sucker” speech at Henry’s school.

He told the headmaster: “I’ve given a lot of money to this school, Mr Connaver, and I’ve always considered it a privilege to be able to do so. But make no mistake. I am a c***sucker.

“And I don’t mean that in the sense of gay belittlement, as it’s currently come to be interpreted. No. I’m an old-fashioned c***sucker. The more traditional kind.

“The kind who f**** over anyone who hurts me, or a loved one. You speak of ugliness Mr Connaver. You have not yet met ugliness.”

That’s one heck of a heavy parent-teacher meeting. But just how far would Franklin go to protect his daughter?

Henry Fraser

Henry, played by Noah Jupe, is a typical teenager, paying little attention to his parents and keen to get his own dog.

He goes to school every day and enjoys playing his violin.

We know that not too long ago he saw his father chatting intimately with Elena outside the school gates, but failed to tell his mum.

We now see him torn between anger at his father for breaking up the family and hoping everything will eventually go back to normal again.

He bangs into Miguel at school, and apologises, but could he be saying sorry for more than just a knock?

He’s obsessed with the case, watching TV footage around the trial on his mobile phone 24/7.

The discovery of a sculpting hammer in his violin case would suggest he may know more about the murder than he’s letting on.

We’re told by Grace that Henry would do anything for his dad, but just how far would he go?

Sylvia Steineitz

Grace’s best friend, Sylvia (Lily Rabe) lends her ear to Grace and offers her advice. The fact she is a lawyer means she also has some insight into the workings of the trial.

She knows the ins and outs of the defence and prosecution teams, and even comes along to court as moral support – or could there be more to it?

We know Jonathan approached Sylvia to defend him when he was dismissed from the hospital. And she also knew about his affair.

However, she hid both facts from Grace.

We’ve also seen that Sylvia wasn’t Elena’s biggest fan – she considered her breastfeeding during a conference committee meeting to be a “hostile” act.

Could there be more to Sylvia and Jonathan’s relationship than meets the eye? And might she have her own reasons for wanting Elena out of the picture?

Wild card: Miguel Alves

Miguel (Edan Alexander) is Elena and Fernando’s son, and it was while he was receiving cancer treatment in hospital that his mother first met Jonathan.

Miguel is now doing well, and back at school – but could he have known more about his mother’s relationship with his doctor than he let on?

He was the first one to find the body after skipping school to check on his mum. We see him running home to alert his father – but is that the full story?

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Could he have been jealous of his mother’s new partner? Aware that his baby sibling wasn’t his full sister? And upset that his dad was being cheated on?

Could something else have happened when he arrived at his mother’s studio?

While we don’t yet know the identity of the killer, one thing we know for sure is that someone is lying.

The Undoing concludes tonight at 9pm on Sky Atlantic and is also available on NOW TV.