Note: This post discusses plot details from various episodes of HBO’s “The Undoing.” Possible spoilers ahead.

HBO’s “The Undoing” is a perfectly fine six-episode miniseries about a couple, Grace and Jonathan Fraser (Nicole Kidman and Hugh Grant), whose marriage and privileged lives implode when Jonathan is accused of murdering his mistress. The plot, based on a novel by Jean Hanff Korelitz, is standard fare for a David E. Kelley drama. Kidman and Grant, veteran actors who both played deliciously evil “Paddington” villains, are the obvious draw.

The acting is indeed good. Grace’s coats (you must have heard about the coats) are fabulous. But no one in the show shines more than Kidman’s steely baby blues, which quickly become a character of their own.

The eyes have it from the very first episode, where they serve mostly as a focal point in scenes with Elena (Matilda De Angelis), a young mother whose child attends school with Grace and Jonathan’s son Henry (Noah Jupe). Grace’s friends greet Elena with a mix of jealousy and disgust over her youth, beauty and lack of wealth, but Grace’s eyes hint at something else: intrigue, perhaps, or longing for her 20s.

The something else remains even as Elena comes on a little strong, striking up a conversation with Grace while standing naked in the locker room at their gym and, later, when a visibly upset Elena kisses Grace on the lips before leaving a swanky school function.

When Grace gets a call informing her that Elena has been murdered, Kidman’s widened eyes appear to singularly process the news. At this point, the viewer can only speculate what we learn in a later episode — that Jonathan had been having an affair with Elena, and fathered her youngest child in the process — as Grace’s eyes dart back and forth in horror and something else. Is it suspicion? Guilt? Dread? Grace is startled when she is approached by two detectives investigating Elena’s murder and, again, we rely on her icy glare to tell us what she might be thinking.

We know the HBO drama isn’t the first project to focus on Kidman’s most expressive feature — the poster for Stanley Kubrick’s 1999 drama “Eyes Wide Shut” features Kidman peering out from a sensual kiss with then-husband Tom Cruise. But “The Undoing” takes this silent communication to a new level. Have eyeballs ever been so central to a standout performance? Can they win awards? Because Kidman’s are doing the work.

This is especially true in the final scenes of the “The Undoing’s” first episode as Grace tries to reach Jonathan, who is away on a business trip, to discuss Elena’s murder and how such a trauma might affect their son and his classmates. After leaving several voice mails, Grace discovers Jonathan’s cellphone in a bedside drawer. Kidman’s eyes dart around nervously and more ambiguously than ever as she calls hotels in Cleveland looking for her husband. The camera zooms in on one erratic eyeball as Grace spells their last name slowly: F-R-A-S-E-R.

When Grace fails to locate him, the whodunit moves forward in a predictable fashion. But the episode’s last shot zooms in once more on Grace’s eye, still trying to piece it all together. Her eyes similarly carry the second episode, which follows Grace as she tries to find Jonathan while fielding increasingly specific questions from detectives. When Jonathan finally resurfaces and confesses the disturbing truth about his relationship with Elena, whose eldest child was one of his oncology patients, we close yet another chapter through Grace’s eyes, teary and exhausted on a call to the authorities.

By the end of the third episode, it’s clear that focusing on Grace’s impenetrable stare is intentional. She looks on in horror as detectives confront her with photographic evidence placing her near the scene of Elena’s murder around the time the young mother was slain. In the following installment, Grace watches as Jonathan confesses his enduring love for Elena on national television (via a fictional show hosted by Connie Chung). Though the episode ends on a close-up of her husband’s eyes, Kidman’s remain our window into Grace’s shock, her betrayal — her, well, undoing.

The show comes to a not-entirely-unpredictable climax in the penultimate episode, when Grace happens upon the murder weapon in her son Henry’s closet, after uncovering unsettling information about her husband and his life before they met. Her panicked eyes hint at the complicated feelings a mother might have in that situation — fear, the need to protect, desperation, guilt (the title of Korelitz’s book is “You Should Have Known”).

Kidman recently told TV Line that director Susanne Bier, who helmed all six episodes of the series, hadn’t told her about the close-up shot at the end of the show’s pilot, an approach the actress described as “where she almost goes into my head. It’s like, ‘Oh my God you’re inside me.’ ”

But, the actress said, that vulnerability served a purpose. “I was like, ‘Whatever you need to do to tell this story so that people will feel it,’ ” Kidman recalled. “'Not just watch it from a distance but go on a journey and feel it.' That’s what we hoped for.”

Elena’s killer was revealed on Sunday’s episode, and it wasn’t the twist ending many of us were hoping for. Still, it was a wild ride that ended with the camera fixed on Kidman’s eyes, glancing upward (in a helicopter, because this is a show about rich people).

“I love the end shot because there’s a woman who has now got the next stage of her life, and what does that mean?” Kidman said in HBO’s post-episode vignette. “There’s a freedom in that.”

There’s also mystery, reflected in Kidman’s ever-inscrutable gaze.

Read more: