'Promising Young Woman' Ending Explained by Director Emerald Fennell (Exclusive)

Promising Young Woman
Focus Features

'It was the only way,' Carey Mulligan tells ET of the film's 'brutal' twist.

Spoilers for the ending of "Promising Young Woman" follow.

Writer-director Emerald Fennell knows the ending of Promising Young Woman will be polarizing. The film as a whole -- a revenge movie about a rape culture vigilante -- is primed for discourse, but it's the final act that will be the most talked about. Yet, for Fennel, it's the only ending she ever considered.

The promising young woman of the title is Cassie (Carey Mulligan), whose best friend, Nina, was raped while the two were in school and then committed suicide. Cassie subsequently drops out and begins cruising nightclubs, pretending to be blackout-drunk until a self-proclaimed nice guy willing to take advantage of her picks her up. When each guy is surprised with her sobriety, he's also forced to take a sobering look at himself and how good of a guy he actually is.

It's an avenging mission in Nina's honor, but when a guy from Cassie's past comes back into her life, she's sent on a path of vengeance specifically targeting the people involved in Nina's rape -- the dean who dismissed her, the girlfriend who didn't believe her, the attorney who helped make it all go away -- and the rapist himself, Al Monroe (Chris Lowell), as well as the guys who egged him on from the sidelines.

In the film's final act, Cassie tracks Al down at his bachelor party, held at a remote cabin in the woods. Donning a latex nurse's outfit and posing as a stripper, she drugs all of Al's buddies with spiked liquor before luring the groom-to-be upstairs and handcuffing him to the bed. But when Cassie reveals who she is and attempts to get Al to confess what he did, he manages to break free and smothers Cassie to death with a pillow.

"I think like everyone, when I was first writing it, I expected and wanted the ending that we all expected and wanted," Fennell tells ET. "You're expecting for her at any moment to get out a machete, get out a gun and do this stuff that we're used to seeing in movies like this. But once I was there, it wasn't possible. It wasn't honest. Women do not resort to violence very often, if ever -- that's one of the main tropes of this genre that is subverted -- so it was important to me that the moment a woman is in a room and there's a weapon and there's a man there, there's really only one way."

Mulligan agrees. "It was the only way," she weighs in. "I found the ending very difficult and very satisfying. It was such a brilliant ending to the film... I absolutely felt in line with Emerald that you have to tell the truth about this kind of stuff, and it would be a lie to do anything else."

Promising Young Woman, in the end, is not a revenge fantasy. The crusading heroines of those films don't die in the end -- especially not at the hands of a villainous male character -- but this is a story about the reality of what happens in the pursuit of revenge.

"I think the movie itself had to be honest about how dangerous this journey was and how hard it is to win in these circumstances -- in an allegorical sense as much as a specific sense, like, it's so f**king hard to win, isn't it?" Fennell continues. "It's brutal, but I made a decision to make it feel as real to me, [and] that was the only way out, I think. She knew there was a risk, so she'd made a contingency plan for if something went wrong."

The next morning, Al and his accomplice, Joe (Max Greenfield), burn Cassie's body. And while there is no happy ending here, Cassie, promising young woman that she is, had a Plan B in the case of her disappearance: She sent all the evidence to the aforementioned lawyer and pre-scheduled a text message to be delivered during Al's wedding reception as police arrest him for her murder.

"We're used to men putting their lives in danger for a good cause. I think we feel disappointed and robbed if women do it, but I've always felt her journey is incredibly brave," clarifies Fennell, emphasizing that she does see Cassie as having a death wish. "I don't think she meant for it to happen the way it happened -- in the same way that we didn't want it to -- but she knew there was a chance, because she's not an idiot."

"[But] I didn't want an ending that's sort of bogus with her leaving, smoking a cigarette with a burning building behind her," she concludes. "Of course, we all wanted that. But then you leave the movie theater, and you say, 'That was nice.' You don't get that feeling that we all feel in these circumstances which is, it's so unfair. Because it's still so unfair. That's the reason for the ending."

—Additional reporting by Ash Crossan