Jessica Henwick based her Glass Onion character on her time as a production assistant

Jessica Henwick was determined to never be an assistant again. Until she had to play one in a film.

Henwick (Game of Thrones, Star Wars: The Force Awakens) joins the ensemble of Glass Onion: A Knives Out Mystery as Peg, the long-suffering assistant to supermodel Birdie Jay (Kate Hudson). The actress, who began her career behind the camera, had plenty of personal experience to draw from.

"I've been a P.A., so I knew what it was like," she says, while joining EW for our Around The Table . "I quit. I walked off. I was like, I'm done.'"

Henwick continues, explaining that she'd been working as a production assistant in the set-decoration department of a film when she was pushed to her breaking point. "One day we had this wedding scene, and so we had to blow up 2000 balloons," she recalls. "We finished the full day of work. and the wedding was the next day and the tanks hadn't come. We were like, 'We've got to blow up 2000 balloons manually.' I did it the entire night and I pulled an all-nighter."

Jessica Henwick
Jessica Henwick

Kanya Iwana for EW Jessica Henwick

Though the actress won't reveal what film this was for, she does cite it as a particular grueling night in her career. "It got to 6:30 a.m.," she remembers. "And I had just finished and I was dying. And an actor walked on the set and she was like, 'Oh, my God, it's so early.' I literally went, 'I quit.' I walked off the film."

Luckily for Henwick the experience came in handy while developing her Glass Onion character. "I tried to capture that feeling that I had that day," she reflects. "That's how Peg feels every single day. Just right on the verge of quitting. 'Why am I doing this?' But also she just can't get out of it, because she loves and is reliant on Birdie. It's a very interesting, fascinating relationship. Super co-dependent. We don't get to see women in this relationship very often on screen."

When she first signed on to the project, Henwick says her character was the biggest blank slate of any of the Glass Onion ensemble. But that just gave her more room to play. "She's not written as someone who doesn't like her job," she told EW previously. "I was like, this is not going to be interesting if this is a woman who enjoys this job. This is probably someone who's tried to quit three or four times, and can't bring herself to do it. It's like a toxic, love-hate dynamic between the two of them. Peg despises working for Birdie, but Birdie can't live without her. And Peg knows that. And Peg loves her."

Oh, and those days as a P.A. weren't all bad — Henwick once wrote Glass Onion writer-director Rian Johnson a fan letter when she was still a film student. And when she got an email from Johnson telling her she had landed the role of Peg, it appeared as a "recognized e-mail" in her inbox.

How's that for a little whodunnit kismet?

Glass Onion: A Knives Out Mystery is now playing in theaters for a limited one-week engagement until Nov. 30. It hits Netflix Dec. 23.

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