In “Oppenheimer,” the writer and director Christopher Nolan’s summer blockbuster biopic — three words that generally don’t go together — the character of Kitty Oppenheimer is effaced twice over.

Kitty, played by Emily Blunt, is the woman behind the man: Though a scientist herself, she is the sidelined wife of J. Robert Oppenheimer (Cillian Murphy), the American physicist who led the development of an atomic weapon during World War II at Los Alamos, N.M. “Oppenheimer” is emphatically his movie, so much so that a lot of the script was written in the first person (“I OPEN my eyes- JUMP out of bed- SCRAMBLE to dress”).

And second, though Kitty was Robert’s wife (they had two children together), she was not his first love nor, the film suggests, his strongest. The psychiatrist Jean Tatlock (Florence Pugh) was initially involved with Robert for three years, and the two continued to see each other, even after the Oppenheimers were married. Midway through the film, Kitty finds her husband manic over her death.

“How heartbreaking it must have been for her,” Blunt said, “to see him in that kind of state about another woman.”

It is all to say that Blunt, the London-born actress known for films such as “The Devil Wears Prada,” “Mary Poppins Returns” and “A Quiet Place,” might have disappeared into the three-hour epic, which was based on the Pulitzer Prize-winning biography “American Prometheus.” But Blunt’s is among the most memorable performances in a film packed with movie stars and acclaimed character actors. The winner of a Screen Actors Guild Award for “A Quiet Place” in 2019, Blunt is now a likely candidate for her first Academy Award nomination.

In a video interview last month, she talked about sympathetically portraying an unfortunate but not exactly likable character. These are edited excerpts from the conversation.

Christopher Nolan asked actors to learn about their real-life characters. What about Kitty Oppenheimer informed your performance?

We all read “American Prometheus.” On the flight out to Albuquerque, I could see other people trying to cram it. The wives in Los Alamos described her as being one of the most evil people they’ve ever met. Men were intrigued by her but a bit intimidated. Kitty didn’t do small talk. She only did big talk.

Robert and Kitty Oppenheimer temporarily offloaded their baby son to their friends, the Chevaliers, because they were so overwhelmed. Was that scene difficult to perform?

I have 9- and 7-year-old girls, and I adore being a mom. I’ve always really loved kids. So it’s quite hard to be so cold-shouldered with these little ones on set. Kitty’s clearly got trauma there — trauma that wasn’t named at the time. She has descended into drinking too much. I tried to empathize with the woman who was in possession of a phenomenal brain herself, who is having to contort herself into the good housewife-y. It must have been agony for someone like her, who was so wild, so brilliant, should never have been a mother, and clearly had huge depression after the kid was born.

How do you balance empathy with being true to the character, potentially at the expense of likability?

For me, it’s never important if someone is likable. I just have to understand them. I could play that quiet desperation of the character, the restlessness and that unashamed flair that she had, which was so fiery and exciting. And yet she was this very stabilizing force for him. She was his most vigorous protector. I think she had rather extraordinary qualities, as well as ones that really let her down as a person. She is abrasive and flawed, but I really sympathized with that idea of someone deteriorating at the ironing board, when she should have been made for intellectual endeavors that would have thrilled her.

Were there any other scenes that unlocked Kitty for you?

Do you remember the scene under the rock with Cillian? He’s gibbering with incoherence about his lover.

When I read the scene, I was like, “Wow, that’s so interesting, it’s almost like he can’t see that he’s speaking to his wife.” And I slapped him — Chris was like, “Slap him.” It’s not in the movie, but I hit that famous cheekbone way too many times. Maybe what I played more is her attempt to save face. Like: “Pull yourself together, people here depend on you.” It’s more like, “I depend on you.”

How did the unconventional, first-person nature of the screenplay influence how you approached the role?

It was made clear to all of us that this is a single perspective. Oppenheimer’s character is going to reach through the screen and pull you inside of his head, and you’ve got these rather more wild, colorful characters around him. We were there to emotionally elicit different sides of this character.

I interviewed Nolan shortly before “Oppenheimer” was released about the IMAX 70-millimeter format.

It must have been like Dork Central for him. The passion about film is infectious.

What was it like shooting with the IMAX cameras?

It would be brought in like a massive fridge. And it’s loud: It sounds like Chewbacca coming in. There’s something freeing, because you know that it’s going to capture every little flicker and nuance on anyone’s face. But it is loud, and at first you’re like, “How am I going to function?” It’s the understated nature of Chris’s sets, the focus and lack of chaos, that it was never this declamatory moment when the IMAX would come in.

How would you contrast Nolan’s “calm” sets with others you’ve been on?

On some sets you’re flying by the seat of your pants. It can work both ways: With a comedy or something that’s more free-spirited, sometimes it’s great for it to be a bit more chaotic. But with Chris, it’s his preparation, so that when you show up, you don’t feel rushed as an actor. I’m sure the crew was horizontal every night by 7 p.m.