Repulsion is riveting and troubling. Roman Polanski’s 1965 near-masterpiece follows Catherine Deneuve’s Carol, a young woman whose shyness and dislike of men, over a long stretch of unwanted isolation, worsens until it reaches a feverish, hallucinatory peak. The film isn’t particularly interested in what clinical diagnosis would apply here, nor–besides one haunting implication towards the end–in any other kind of explanation. At its best, it’s grounded instead in the slippery psychological atmosphere of Carol’s own mind, in her experience of an increasingly distorted reality.

Early on, Carol has a few landmarks she can use to navigate her way through the fog of fear and, yes, repulsion. She has a job as a manicurist at an elaborate salon, a “safe” territory few men venture into (but one often haunted by mentions of them). Even there, she’s prone to slipping away from the concrete world around her, but–at first–she can still pull herself back. It’s like she’s in a pool that’s constantly getting deeper and murkier, but in certain places, with help, she can still touch the sides to keep herself from sinking.

The most grounding part of her life, however, is her older sister, the chic and worldly Helen (Yvonne Furneaux). She’s lively and active where Carol is dreamy and disengaged; she’s unrepentant, unabashed, and direct where Carol is defined by the need to retreat and muffle herself in vagueness. Carol forgets to pay the rent; Helen deliberately dodges it as long as she can and then doesn’t flinch away from the landlord’s anger. They don’t always agree–Carol makes no secret of disliking Helen’s married boyfriend (Ian Hendry), for one thing, and Helen seems to find her judgment irksome and her neediness suffocating–but they have a life together, and a fairly normal one at that.

That normalcy is a shield that protects but also denies. It’s easy for Helen to categorize Carol’s illness as an annoyance rather than a problem, to think, My bratty little sister threw my boyfriend’s toothbrush and razor away because she hates him, rather than grapple with the almost atavistic revulsion Carol feels at seeing Michael’s private, bodily toiletries so close to her own.

And then Helen and Michael leave on a long trip, and Carol is alone. This is where the subtle suspense of the movie cranks up into more visceral psychological horror. There’s a crack in the wall of her flat, and she keeps imagining it widening and branching out. There’s a young man, Colin (John Fraser), who loves her enough to make excuses for her strangeness but not enough to leave her alone when she cringes away from him. People overwhelm her; time gets away from her. The flat is made repugnant by Michael’s leavings, with stray shirts like droppings. A raw, skinned rabbit for a dinner that never happened becomes a kind of talisman for her, as vulnerable and festering as her own state of mind. She has nightmares and hallucinations, but they’re not necessarily any more terrifying than what actually unfurls–Carol dreams of men who won’t leave her alone, and she wakes to them, too. That’s part of the horror: she’s not wrong about the world, not really, not entirely. There are more than enough grasping men out there to realize all her fears.

If Repulsion has a major fault, it’s in Deneuve’s styling. Early on, Carol’s incredible beauty plays like a curse: she longs to be left alone, but she looks like Catherine Deneuve. She can’t escape attention and assumptions. It’s a deliberate part of the narrative–or so you might think until the last act of the film. By then, Carol has been holed up in her flat for days, almost completely disconnected from reality. There’s a dead body moldering in her tub, so it’s hard to believe she’s bathed. This is not a woman who is practicing good self-care. But Polanski insists on Carol’s beauty even as she’s falling apart–no greasy hair, no haggard face. That refusal to let her inside turmoil make her less photogenic does, I think, damage the film in a small way. The need to keep her beautiful even as she’s suffering, past any point where that would make sense, begins to seem fetishistic rather than poignant.

That said–with spoilers for the end–I can almost excuse it, because keeping Carol as beautiful as ever does allow for the knife-twist of the scene where Helen and Michael finally return home. Carol, hiding under the bed, catatonic and surrounded by horror and ruin, is, of course, still gorgeous–still touchable, and no longer present enough in her own mind to resist touch. Michael scoops her up, carrying her away to help–but there’s a small smile on his face as he looks down at her, as the girl who never liked him, who was always disgusted by him, lies limp and pliant in his arms. She’s still beautiful, but she’s finally a beautiful object, able to be handled at will. From a certain societal point of view, one that haunts Repulsion like a ghost, that’s a happy ending.

Repulsion is streaming on Tubi and Amazon Prime.