A bunch of drunk dudes at a bar see a beautiful young woman sitting across from them – or trying to. Cassie (Carey Mulligan) is so drunk she's barely conscious, falling over in her seat, hardly able to keep her eyes open and repeatedly failing to get her phone out of her bag to call an Uber.

One of the men approaches Cassie and even though you hope he's going to be a gentleman about it and see her safely home, it turns dark as he instead takes her to his place, plies her with more alcohol and doesn't bother with any form of protest as he starts undressing her, even though she repeatedly asks what he's doing in a slurred voice.

All at once, from an overhead shot, Cassie's eyes snap open, staring straight into your soul. She sits up, completely lucid, and says loudly and clearly to the creep who's been assuring her it's okay and that she's safe; 'I said, what are you doing?'

Cassie is a woman on a mission, and as her story progresses we learn more about it. She works a dead end job in a coffee shop after dropping out of medical school years earlier where she had a real future, and her current pastime of luring men away for what they think is an easy lay before calling them out on their behaviour is on behalf of someone we know only as 'Nina'.

It's not hard to work out that Nina, Cassie's friend, was the victim of a rape while at college and – though it's never referred to directly – killed herself, unable to face the trauma. Cassie has likewise checked out of life, still living at home with her understanding but exasperated parents and refusing to move on with her life.

Instead, she's in the business of exacting vengeance on a society and system that not only let Nina's rape happen but is trying to expunge her name from history. Cassie's most satisfying mark might even be the dean of the college, the slickly professional Ms Walker (Connie Britton).

After defending her original stance that there just wasn't enough evidence to charge or convict, Walker's confidence crumbles in an instant when Cassie tells her where her daughter is.

We've already seen her virtually abduct the young lady with vague promises of a music video shoot with her favourite band, and Walker now faces the horror of believing her daughter is with the men who raped Nina. Evidence, as her pleading and terrified face reveals now, be damned.

But Cassie isn't the Terminator, and she can't help but wonder if her mission of revenge is quietly destroying her, especially when cute former classmate Ryan takes a shine to her at work and pursues her.

She agrees to go out with him and despite herself Cassie starts to fall for him. When she goes to visit Nina's mother and even the latter tells her it's time to put Nina's memory to rest and move on Cassie seems to decide to join the land of the living again – even when Ryan reveals that Al, their classmate and the one who raped Nina, is getting married soon.

But her story turns on a dime, and Promising Young Woman is ultimately like an 80s action film. How?

Her budding relationship with Ryan has run into trouble because he's seen her leaving a bar with another guy from their old circle, dressed up to lure him into her usual trap. She tries to explain but Ryan wants none of it, rejected and hurt.

But as soon as she gets close enough to repair things, a revelation hits like a bomb. Courtesy of another of her victims, Madison (Allison Brie) – who Cassie's tricked into thinking she's slept with a complete stranger while passed out drunk in a hotel so she can see how it felt for Nina – there's actually a video of the assault.

And when Cassie watches it, she hears to even greater horror that Ryan's voice is on it. He was there watching Nina's rape along with all their friends, not only doing nothing but yelling encouragement.

It's an 80s action film because it's where the hero finds and makes peace with his (it was never usually a woman) purpose at the start of the third act, and that purpose is vengeance.

As Denzel Washington says in Man On Fire when asked what he's going to do now after his job as a protector has failed and the story seems at an end; 'kill them... everyone who was was involved, everyone who profited from it, everyone who looks at me wrong'.

Cassie's face sets and she becomes the personification of revenge. She might now be at the point where her soul is truly lost for what she's about to do, but in Nina's name she's going to burn them all to the ground.

If it was a corny action romp it would be the 'now it's on' moment that brings a gleeful smile to your face... and to be honest it does here too. As much as you want Cassie to live a normal life, you want the villains – and they're all villains – to pay.

She makes her final stand at Al's bachelor party, posing as a stripper, and even with what becomes of her (which I won't reveal here because it's as heartbreaking as it is poetic) she has the upper hand until the very end. I loved Cassie because she outsmarted everyone.

Like another recent watch, Emily the Criminal, it's a fantastically told story that manages to layer social comment into the narrative effortlessly.

It's a story about about a woman exacting revenge for her friend being raped on everyone who did it, allowed it to happen or let it go unpunished, but it speaks volumes about rape culture.

'I'm not a bad guy', Al keeps crying when Cassie finally has him where she wants him, and the script takes pains to point out how the people who do (or abet) such things are just that – people, not drooling monsters.

But there's one more sociological dimension writer/director Emerald Fennell herself might not even have intended. As a society we find it easy to ignore and reject the extent of sexual assault – that's one of cornerstones of rape culture itself, after all – but it's very hard to ignore murder or suicide simply because we're left with a dead body.

By watching it and sympathising with what Nina went through, are we subconsciously subscribing to the rape culture narrative that she's only really a victim because ultimately she ended up dead, that if she was 'just' raped we'd be able to sweep it under the rug and protest that there wasn't enough evidence (like Walker) or that despite raping a young woman we're a good guy (like Al)?

Whether Fennell intended that line of thought or not, Promising Young Woman not only provokes you to think, it's the best example of a film that does so in a long time.

I haven't seen Mulligan on screen in quite awhile but like she is in every role, here she barely breaks a sweat portraying a character as real and situated in the world as you could hope to see in a screen story. She, the script and the whole thing are scary, unnerving and thoroughly brilliant.