‘Promising Young Woman’ is an unexpected turn for Carey Mulligan – that’s the point

It had to be Carey Mulligan. Writer-director Emerald Fennell had just seen her in “Wildlife,” Paul Dano’s directorial debut about a woman trapped in an empty marriage in 1960s Montana.

The performance sparked the same sense of awe Fennell felt after “An Education,” the 1960s coming-of-age drama for which Mulligan, 35, earned an Oscar nomination a decade ago. Steve McQueen and the Coen brothers directed her in between, a span of her career that also included an acclaimed supporting turn in the art-house thriller “Drive.”

The English actress’s roles were diverse, but her inimitable screen presence threaded them together. She has a certain quality to her, Fennell said in an interview with the Washington Post. No matter how quiet the character, you don’t mess with her.

So when the time came for Fennell, also 35, to cast the lead in her own feature debut – “Promising Young Woman,” whose protagonist seeks to avenge her lifelong best friend’s sexual assault – she knew Mulligan could strike the right tone.

“There’s something so exciting about someone who only does the stuff they want to do, and it’s a treat to see them,” Fennell said. “She’s so interesting, Carey. … I just had a feeling that she would be incredible, and, honestly, the fact that she said yes, I was blown away.”

At first, “Promising Young Woman” might seem a surprising choice for Mulligan. Perhaps it’s the candy-colored aesthetic and blaring pop music, a stark contrast with the sober hues and tone of, say, “Inside Llewyn Davis.”

People often think of her as a period actress these days, Fennell said – nodding to the streak of films that also includes “Suffragette” and “Mudbound” – but she hasn’t always existed in that space.

You could argue that Fennell’s film is deceptively bubble gum, a layer of sugar coating its sour core, a taste we more often associate with gut-wrenching work. But that’s just the point, according to Fennell: Who’s to say all the girly stuff isn’t serious, too?

“Nobody suspects the person with the multicolored manicure to scratch their eyes out,” she said.

Fennell subverts genre conventions – par for the course with the director, who helmed the second season of BBC America’s “Killing Eve” – while Mulligan’s character, Cassie, surprises those around her. Her projected femininity allows her to hide in plain sight.

Having dropped out of medical school, Cassie spends her days as a barista and, at night, swings by bars, trolling for self-proclaimed nice guys – the same sort who assaulted her friend, Nina. She pretends to be blackout drunk, and the men offer to take her home, only to try to take advantage of the nearly unconscious woman they just met. Then, when they least expect it, Cassie snaps back into an alert state.

Mulligan’s decision to play Cassie came down to “just feeling like I wanted to do it,” she said in a separate interview. She recalls getting continually “wrong-footed” by the script, drawn into its humor and romance before it turned dark “within half a page.”

The shoot lasted just over 20 days, during which Mulligan threw herself into Cassie’s fury (but not to the extent that she took the character home with her, she said, beyond the Barbie-esque nails and blonde hair extensions).

“It’s a similar reason to why the Coen brothers thought it was so funny to cast me in ‘Inside Llewyn Davis’ as a sort of enraged woman,” Mulligan said. “I suppose people can get to know you from a certain performance, and it can be hard to break out of that sometimes.”

Fennell set out to defy expectations with her supporting cast, as well, selecting beloved figures to play the secretly skeevy men. Former teen heartthrob Adam Brody (“The O.C.”) appears at the very start, with “New Girl” favorite Max Greenfield popping in later on.

Comedian Bo Burnham plays Cassie’s former classmate, Ryan, her love interest and, she hopes, the sweetheart to redeem his gender. But the quest for vengeance doesn’t stop at the gender divide, as Cassie also targets women she considers complicit in the crime against Nina – including one portrayed by Connie Britton.

Rather than choosing one villain, Mulligan said, the film is “much more about our general approach to this kind of stuff as a society and a reaction to what we’ve grown up with.”

“Women have played a part in that,” she said. “We’ve all bought tickets and laughed at comedies that have made this stuff seem really trivial and funny for so long.”

Cassie’s own actions aren’t immune to criticism, Fennell said, which is where Mulligan’s strengths as a performer come in.

Beneath all the glitter, “Promising Young Woman” is a portrait of grief, of a woman whose revenge plot has gone from noble to “miserable.” Cassie has spent years hanging onto a ghost, continuing to torment herself almost as much as she does the men.

Fennell and Mulligan chatted about their childhood best friends to build out a backstory for Cassie and Nina, who never appears in the film. The actress declines to expand on the imagined story, noting that the mystery is “why film is so interesting – what you don’t see or hear is almost as important as what you do.”

Nina’s physical absence is just as deliberate; she is a constant presence in Cassie’s mind. “What (Cassie) does is an addiction,” Fennell says. “She stays on this road that is miserable and lonely and cold and dangerous. But there’s this other one, which every single other person is saying, ‘Look, it’s rainbows and sunshine and love,’ and all of that fluff.

“We all, as an audience, want her to choose that path, too. It’s about showing how hard her journey is.”

Mulligan was daunted at first and admits that she wondered whether Fennell – an actress herself, most recognizable to American audiences as Camilla Parker Bowles in “The Crown” – ought to play Cassie instead. Mulligan tends to call cut on herself mid-take, a habit she says Dano helped curb on “Wildlife” by encouraging her to channel her self-doubt into the character’s state of mind.

She returned to this advice for a scene in “Promising Young Woman” in which Cassie runs into Ryan mid-scheme, faking drunkenness outside a bar with her arm around another man. She straightens up immediately, her usual confidence traded for deep shame. Mulligan was having one of those nights when “just everything feels wrong,” she says. But then she realized that’s exactly what Cassie felt.

“In film, a lot of the opportunities that have come my way have been much more in a sort of serious, domestic space,” Mulligan says. “I’ve become really interested in the last couple of years in these kinds of characters … where women are allowed to be flawed and troubled by things and behave in ways we don’t necessarily agree with, even. But we still root for that person.”

“Promising Young Woman” premieres Friday at area theaters.