HBO’s “The Undoing” wrapped up its murder mystery with a killer betrayal.

Warning! Spoilers ahead!

Jonathan (Hugh Grant) killed Elena (Matilda De Angelis).

Flashbacks finally revealed the full extent of Elena’s last moments.

After having sex, Jonathan demanded that she stay away from his family and seemingly ended their affair.

Elena went after him with a hammer, saying that he would never leave her, that it would never be over between them.

Jonathan grabbed it from her – and beat her to death.

Henry (Noah Jupe) found the murder weapon at the family summer home, put it through the dishwasher – twice! – and hid it to protect his dad.

Grace (Nicole Kidman) was horrified when Jonathan suggested that Henry could be the actual killer.

That was probably the moment that anything good between them died, if either one of them could see it.

Grace could see how well the trial was going for Jonathan and opted for the nuclear option.

She enlisted her pal Sylvia (Lily Rabe) to help the district attorney impeach her own testimony.

That bit happened mostly off-camera.

But Grace shocked Haley (Noma Dumezweni) and Jonathan when she volunteered to testify on his behalf.

She promised she was just going to tell the truth: That she thought Jonathan could never do it.

Jonathan was thrilled; Haley was skeptical.

But Grace delivered an outstanding performance, telling the jury that in her professional opinion, Jonathan was an empathetic healer and not a violent man.

Then the district attorney got started.

She played back Grace’s frightened 911 call – jurors could hear in her own words how terrified Grace was.

Grace said she felt that way only in the moment, but the damage was done.

Armed with knowledge of her conversation with Jonathan’s mother, the district attorney destroyed Grace’s credibility (with Grace’s help) by having her relive the tragedy from his youth – the death of his young sister – and how Jonathan never felt grief nor remorse, signs of a narcissist.

Haley called for a mistrial, but the judge pointed out that Grace was her witness, so her testimony stands.

Jonathan knew he was right and truly screwed.

Grace walked out of the courthouse with Franklin (Donald Sutherland) and Sylvia.

Hey, it’s no “Witness for the Prosecution,” but it was a satisfying moment.

Jonathan wasn’t done.

The next morning, he tricked Henry into meeting him for breakfast one last time – and took him on a road trip to hell.

Jonathan seemed ready to kill himself and take his son with him.

As they dodged traffic – barely – Jonathan told him his legacy would always be Henry and his patients.

With the police closing in on him, with Grace arriving by helicopter, Jonathan stopped the car and stood on the ledge of a bridge, seemingly ready to jump.

Henry’s cries meant nothing to him.

But when he heard Grace cry out, Jonathan turned.

“Give me a hug,” he demanded as Grace scooped up Henry.

Was he just waiting for her to arrive? Did he think they still stood a chance together? Was his suicide attempt just another act?

Would a true narcissist end his own life?

The police took him away, and Grace and her family took to the skies again.

Random notes:

It would have been nice if David E. Kelley’s script had given us a final moment between Grace and Jonathan – something that had her finally claiming her power and her truth, and asserting her freedom from Jonathan. That lack of catharsis hurt.

Under Susanne Bier’s direction, Kidman’s Grace seemed like a cipher for so much of the story.

So who was the “other” woman Jonathan had an affair with?

The Emmy folks need to look at Donald Sutherland here. He was so commanding in his scenes.

There was one continuity error: After his son is forced to testify for the defense, Fernando (Ismael Cruz Cordova) storms the private conference room where Grace, Jonathan, and Haley are conferring, and knocks a stack of papers off the table onto the floor.

Police take him out, and when the camera cuts back to a wide angle again, there are no papers on the floor.