In Paul Dano’s Wildlife, which premiered at Cannes’ Critics Week last night after a debut in Sundance, Carey Mulligan plays Jeanette, a woman who responds to her husband’s desertion to fight a fire raging outside their small town by carrying on an affair with an older businessman while her 15-year-old son looks on. Working with first-time director Dano, and co-screenwriter Zoe Kazan, was a draw for Mulligan, but it was the opportunity to play a woman with honest flaws that made her sign up.

“She’s allowed to be wrong, and out of control, and she doesn’t have everything down,” Mulligan told me, at Deadline’s Cannes Studio, of her interest in the part. “Women are so often, on screen, expected to be perfect in the way that they look and the way they act. It’s rare to see a woman on screen who is unfaithful.”

She called out the tendency to sanitize female characters that she had observed in previous work. “I’ve worked on jobs in the past where we’ve filmed stuff that it’s in the original script or book—where the character misbehaves in a way that isn’t perfect and isn’t model woman—and that’s never made its way to the final cut,” she insisted. “I’ve asked why and they’ve said, ‘Well the audience really doesn’t like it when she’s nasty. They really don’t like it when she’s mean.’ I think it’s so ridiculous, and you can’t see a full person until you see their failures.

“That’s what I liked about Janette; there’s failures throughout in what she’s doing, but hopefully you still feel empathy for her, and her family still love her in spite of it. That felt very real to me.”

She was joined in the studio by Dano and Kazan, who explained their collaborative process. “Paul and I met working together a decade ago, so our first relationship was a working relationship,” Kazan said of her partner. “We rely on each other a lot.”

Dano, she said, handed her a draft that wasn’t really a screenplay, and she insisted on completely rewriting it. Parried Dano: “It wasn’t in screenplay format on purpose.”

Dano’s interest in making his directorial debut with the film stemmed from a similar place as Mulligan’s he said. The film is based on Richard Ford’s novel. “I think it was probably something to do with how he looked at such a heartbreaking or harrowing family situation, but still with love and compassion and honesty,” Dano noted. “I really liked looking at our flaws in full depth but still with a sense of love there.”

For more from Dano, Kazan and Mulligan, check out the video above.