Promising Young Womanopens with an encounter that feels like a fantasy.

If you've seen the trailer, you're already familiar with the scene: Cassie (Carey Mulligan) gets ushered home from the club by a not-so-nice guy eager to take advantage of her heavily intoxicated state.

Then, just as he's about to rape her, she snaps to attention, revealing herself to be stone-cold sober. "What are you doing?" she demands, to his shock and horror.

Watching this reversal, it's hard not to think, If only more collisions between drunken women and lecherous men ended this way. If only the women were never really in danger. If only we could demolish rape culture by scaring the shit out of bad men. If only it were that easy. Oh well. At least we can enjoy it in the movies.

But Promising Young Womanisn't satisfied with the simple pleasures of revenge. Sure, it's fun to watch these would-be rapists tremble before Cassie, particularly when writer-director Emerald Fennell's portrayals of these men feel so bitingly accurate. (Of coursethe wannabe novelist can't stop gushing about David Foster Wallace.) She's heard it all before, and we laugh because we have too, and then we cheer because fuck these dudes.

As the film goes on, though, the jokes become more jagged, and the thrills more troubling. The deeper we go into Cassie's world, the more difficult it becomes to ignore the blood and bruises underneath her hard candy-colored shell, to shrug off all the ugly reasons whythat first scene feels so delicious — what it tells us about Cassie that she feels driven to do this, and what it says about us and our world that we need her to so badly.

Promising Young Womanmorphs into something more unexpected and complex, shifting in shape and tone a few times over its nearly two-hour run time. A cloud hangs over even its sunniest moments, and some its darkest reveals land with a bark of laugher. Its target widens from abusers to enablers (complicit women get their comeuppance, too). Through it all, however, Fennell's confident direction and taut script ensure that its perspective and its mission remain clear.

The sights and sounds of Promising Young Womanare unabashedly girlish. Cassie is costumed in floaty floral dresses and sweet little hair bows, and notable needle drops include Charli XCX's "Boys," Paris Hilton's "Stars Are Blind," and an instrumental cover of Britney Spears' "Toxic." It's an aesthetic choice that feels jarring at first, and then depressingly appropriate. What's more feminine, after all, than having to deal day in and day out with the horrific ramifications of rape culture?

Mulligan is tremendous as Cassie, who undergoes a few transformations herself — some pretend, some real. Her showiest moments come when Cassie is playing vigilante, her voice nearly a growl as she takes unsuspecting men to task for the crimes they were all too excited to commit just moments ago. But she wisely underplays the true depths of Cassie's rage and anguish, refusing us the relief of emotional catharsis.

What eventually emerges, after all these twists and turns, is a testimony of how a violation can destroy one's faith not just in the attacker or in oneself, but in everyone else around her, and in the very culture that allowed the crime to happen. It does right by Cassie not by lifting her up as an empowered woman getting back at a world that's wronged her — though she can be that, too — but by taking seriously the trauma and anguish that hardened her to begin with.

Cassie, we come to realize, is a woman daring humanity to show her its worst, and finding that although she is sometimes surprised, she is rarely disappointed. Promising Young Womanpunches its way through rape culture with perfectly manicured nails and a sardonic lipstick smile, and in the end, you may find you're the one who comes out bruised.