Katherine “Kitty” Oppenheimer, played by Emily Blunt, had married three times before she met Oppenheimer at a garden party in San Francisco. They married and had two children, Peter, and Toni.

Blunt was intrigued by Kitty’s rejection of social convention or expectation. “Kitty is a character who doesn’t do small talk; she only does big talk,” Emily Blunt says. “She’s complicated, volatile, bewitching all at once. What I really was drawn to with her is that idea of a woman who refused to conform to the sort of feminine ideal of the time, why you need to get married and have children and support your man and that’s your job and that’s all you’re allowed. She just had this defiance against the system that felt so modern. But I do feel that in Robert Oppenheimer she met her intellectual equal. There was genuine respect there. She was such a confidante for him and was his main ally when it came to making big decisions. He leaned on her heavily and her opinion was of paramount importance to him. She herself was a scientist, and she is that prime example of a woman of that time with a brilliant brain that kind of went to waste at the ironing board, and she suffered for it. Yet she believed in Robert, worshipped him, supported him, and was his biggest champion.”