The film features Pugh as Jean Tatlock, a real-life psychiatrist and love interest to Cillian Murphy’s J. Robert Oppenheimer.
Florence Pugh and Cillian Murphy as Jean Tatlock and J. Robert Oppenheimer walking down the street

Several stars pop during the three-hour runtime of Oppenheimer, including Florence Pugh as Jean Tatlock, the real-life love of Cillian Murphy’s J. Robert Oppenheimer. She leaves a lasting impression despite appearing only briefly in the movie, in moments that include the controversial first-ever sex scene lensed by Christopher Nolan. But the role’s size didn’t bother Pugh—even if the relatively paltry nature of it prompted the filmmaker to apologize to her, the actor says.

“I didn’t really know what was going on or what it was that was being made,” Pugh told MTV UK of being approached about Oppenheimer. “Except I knew that Chris really, really wanted me to know that it wasn’t a very big role, and he understands if I don’t want to come near it. And I was like, ‘Doesn’t matter. Even if I’m a coffee maker at a café in the back of the room, let’s do it.’”

Pugh then met Nolan in New York while she was filming Zach Braff’s A Good Person. “I remember he apologized by the size of the role. I was like, ‘Please don’t apologize,’” she continued. “And then he said, ‘We’ll send you the script, and honestly, you just read it and decide if it’s like…I completely understand the sizing thing.’ And I remember that evening when I got the script being like, ‘I don’t need to…I know I’m going to do it.’”

Described as Oppenheimer’s “truest love” by his close friend Robert Serber in the biography American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer, Tatlock was a medical student and eventual psychiatrist who had a yearslong romantic entanglement with the physicist. Despite his eventual marriage to Kitty, played by Emily Blunt in the film, Oppenheimer would spend time with Tatlock until her sudden death on January 4, 1944.

As shown in the film, Tatlock was found lying on a pile of pillows with her head submerged in a bathtub. Her death would be ruled a “suicide, motive unknown” upon the discovery of drugs in her system and a note that read, in part, “I think I would have been a liability all my life—at least I could take away the burden of a paralyzed soul from a fighting world.” When alerted to Tatlock’s death, as depicted in the film, Oppenheimer took “one of his long, lonely walks high into the pines surrounding Los Alamos,” his biography reads.