Spoiler alert! The following story contains important details about the ending of "May December" (now streaming on Netflix).

Is it possible to ever truly know someone?

That's a lingering question at the end of "May December," the acerbically funny and sneakily devastating new movie from director Todd Haynes ("Carol") and first-time screenwriter Samy Burch.

The film follows TV star Elizabeth Berry (Natalie Portman) as she travels to Savannah, Georgia, to shadow Gracie Atherton-Yoo (Julianne Moore), whom she is set to play in an upcoming movie. Decades earlier, when she was in her 30s, Gracie had been convicted of seducing and raping 13-year-old Joe (Charles Melton), whom she later married and started a family with. As their now-grown kids prepare to graduate high school, Joe begins to process his trauma while Elizabeth attempts in vain to understand Gracie.

USA TODAY spoke to Portman and Moore about the film's ending and that blistering, unbroken-take monologue.

'May December':Julianne Moore channeled Mary Kay Letourneau for Netflix movie

Natalie Portman says her 'May December' monologue was 'such a gift'

Toward the end of the film, Portman delivers a staggering three-minute monologue directly to camera, as Elizabeth reads an old love letter that Gracie wrote to Joe before their relationship was discovered. In the letter, Gracie admits that “we had crossed a line,” but “now, I think I’ve lost track of where the line is.”

After countless hours of studying Gracie’s distinctive lisp and mannerisms, it’s the first time that Elizabeth fully embodies her subject. She cries as she recites the letter alone in her room, throwing her head back in rapture and relief when she finally reaches the end.

“It’s such extraordinary writing,” Portman says. “There’s so much lying and omission of what they don’t say to each other. So to then have this moment of performance as truth, that’s such a gift for an actress. Those moments alone are so precious in this film because they’re such performative people, so you get to actually feel the character when they’re not being watched.”  

In the letter, “we finally get some information through this lens of Gracie," Burch says. "She's not naïve. She's absolutely aware of the legal implications, and she's played that very opposite throughout the film. But also, through Natalie, we see a portal into a woman who is very disturbed. That's not a surprise, but it's still very uncomfortable to look at.”

Portman did eight takes of the scene, all of which were “subtly different but distinct,” Haynes says.

“It was a master class in acting. It was just a remarkable day,” he recalls. “We shot this on the second to last day of the shoot, so there was time for her to absorb Gracie to that degree. It was the scene that I read in the script that made me want to make the film to begin with. And I knew I wanted to shoot it exactly that way.”

Portman was grateful to save the monologue for the end of the 23-day shoot.

“It was really lucky,” she says. “Todd created such ideal circumstances for us to work, and part of that was shooting chronologically. We were able to, in real time, start getting to know and reflect each other in this way.”

Julianne Moore unpacks the movie's ending, unanswered questions

In the film’s penultimate scene, the women have one last encounter at Gracie’s kids’ graduation. Feeling content in her preparation, Elizabeth soon begins to second-guess herself when Gracie asks, “I wonder if any of this will have really mattered for your movie.” Gracie then reveals the lies her son (Cory Michael Smith) told Elizabeth, meaning that she never actually got the full truth.

“For me, the most salient point is, ‘Do you understand me? Do you know me?’” Moore says. “I think that for actors – and for all of us – you only can get so close to knowing another person. That’s what’s so wonderful and so frustrating about being a human. You always want to know more, and you’re always trying to get in there. But there’s always going to be a little piece that’s so mysterious that just belongs to that human being.”

Suddenly insecure, Elizabeth scrambles to find something “real” on the set of her movie. Now done-up as Gracie with a blonde wig and pink lipstick, Elizabeth asks to shoot yet another take before the screen goes to black.

Reading Gracie's letter, "Elizabeth gets to have probably her best moment of acting as Gracie that we think she'll ever do. It's Icarus flying too close to the sun," Burch says. "When we later see her on set, we know that she's never going to feel as confident as she did in that one moment alone in her room."

As for Joe, the last time we see him is at his kids’ graduation, where he breaks down in tears as he watches from afar. It’s up to the audience to decide whether he leaves Gracie or not.

“This is a movie that raises questions,” Moore says. “What’s been wonderful is how many people ask, ‘So what do you think happens? Does the family stay together?’ I can’t answer. The movie ends on an inhale, rather than an exhale.”

The making of the film:Julianne Moore channeled Mary Kay Letourneau for Netflix's soapy new 'May December'

Charles Melton is an early Oscar favorite and the movie's beating heart

"May December" is shaping up to be a major awards contender. Portman and Moore (both Oscar winners themselves) are back in the running for their respective performances, as is Burch for best original screenplay. Melton, meanwhile, is primed to score his first Oscar nomination for best supporting actor, having won at both the Gotham Awards and New York Film Critics Circle Awards this past week.

Melton, 32, is best known for his role as Reggie Mantle in the CW's "Riverdale." Haynes was unfamiliar with the series but was immediately impressed by his audition tape.

“It was different than how I imagined Joe on the page,” Haynes says. Compared to other actors who read for the role, “Charles’ interpretation was more pent-up, more preverbal and more restrained. His looks were almost a distraction when I saw a photo of him before he read the part. I was like, ‘I don’t think that’s going to work. He looks like a model.’ But he did something so exceptional and understood things about Joe that seemed evident in his audition.”

“He’s a marvel,” Haynes continues. “He has much less experience than Julianne or Natalie. Obviously, he’s up against these extraordinary, powerhouse performers. But Charles brings sensitivity, and a physicality around Joe, that’s extremely specific. It’s like a living, fragile performance. His tender little heart is beating right in front of you.”