In the 1990s, Demi Moore was briefly the highest-paid actress in the world, commanding $12 million for Striptease. Moore’s career slowed after that apex, though she’s worked plenty in lots of varied fare, most recently stealing a few scenes as an aggrieved socialite in Feud: Capote vs. the Swans. But it’s been a long while since she’s had a lead role as juicy as her part in The Substance, a gnarly body-horror sci-fi satire that premiered here at the Cannes Film Festival on May 19.

The film, from French writer-director Coralie Fargeat, takes brutal aim at a culture that Moore knows all too well: the terrible pressure placed on women to forever be young and beautiful, reality be damned. Moore’s is a savvy piece of casting in that regard; she’s been put through the media wringer throughout her 40-year career, scrutinized and speculated about and cast aside. Perhaps wanting to vent about all that, or at the very least make a comment, Moore tears into The Substance, committing herself with the fire of someone with something urgent to say.

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She plays Elisabeth Sparkle, a former movie star turned TV fitness guru (an obvious allusion to Jane Fonda) who seems to live a lonely life when she’s not smiling and high-kicking for the cameras. When she finds out that the show’s producers are trading her in for, well, a newer model, Elisabeth procures a mysterious elixir that, she’s promised by a disembodied voice in a video, will create a younger version of herself. But it won’t de-age her like Isabella Rossellini’s serum did for the women of Death Becomes Her. Instead, it quite gruesomely creates a second body from Elisabeth’s DNA. She can spend seven days as the younger being, played by Margaret Qualley, but must keep swapping back to her regular self every other week, lest something bad happen—Elisabeth hasn’t been told what.

Do you, dear reader, think that Elisabeth honors that rule? Of course she doesn’t; would you, given the chance to inhabit a body the world deems so much more desirable? Elisabeth, who goes by Sue when in the new body, gets her job back and quickly ascends the ladder of fame while her old body lies comatose on the bathroom floor or in a hidden closet. It’s a woeful sight, this total abnegation of self to meet societal demands. Elisabeth places demands on herself too, but The Substance does not really investigate the fraught link between internal and external pressures.

Fargeat sets the film in a hyper-stylized version of our world, which maybe undermines the relevance of its message. One longs for the movie to be grounded in more reality so that the mounting surreality of Elisbeth’s private life would stand in starker contrast. Without that nuance, Fargeat can only make points broadly—mostly about plastic surgery and other cosmetic procedures.

In that critique, perhaps too much blame is placed on the women who pursue such cures and, in some cases, take things too far. Funny and gamely ridiculous as The Substance becomes, it is at its core telling a very sad story of a woman destroying herself in the desperate hopes of doing the opposite. Fargeat is resistant to such rumination, though, and keeps ratcheting up the gross-out comedy as the film extends well past the two-hour mark. There are too many endings here, as if Fargeat had several great ideas for final images but couldn’t decide on one. So they’re all thrown in, one after the other, as the film wears out its well-earned welcome.

Moore and Qualley keep selling it, though. Moore especially connects, deftly negotiating an intense transformation that is probably the most physical acting she’s done since G.I. Jane. It’s a thrill to watch an actor go for broke like this, seemingly so devoted to the cause of their film. Fargeat, for the most part, does not fail that determination. The work has paid off, and The Substance was a big crowd-pleaser at this festival.

Which is perhaps something of an irony, given a particular ethos about women and beauty that pervades at Cannes. Here we all are, enjoying a send-up of a system in which we’re also willing participants. I suppose that’s a tragic irony befitting of The Substance, a mean and clever movie that could be sharper but is instead effectively blunt. Maybe, at least, we can all feel a little bit better about ourselves the next time some gorgeous twenty-something strides past on the Croisette—sure it would be nice to be them, but at what cost?