Carol (played by a 20-year-old Deneuve) is a young Belgian woman, who is both repelled and attracted by the idea of sex due to repressed memories. Timid and fragile, she lives in London with her sister Helen (Furneaux). When Helen leaves on a holiday to Italy with her married boyfriend (Hendry), Carol is left alone. Isolated at work too, she shuts herself up in their apartment, and becomes a slave of her own paranoid fears and going psychotic, unable to tell fantasy from reality, and begins to hallucinate. She violently kills a would-be suitor, Colin (Fraser), using a candlestick, and later the landlord (Patrick Wymark) who attempts to rape her. When her sister returns home, she finds Carol under her bed, catatonic, and only a shell of her former self.
At the end, Polanski shows a photograph of the young Carol hinting at a childhood of sexual abuse, which would later resurface in Chinatown.
The apartment is presented as nightmarish: it is full of weird shadows and dark corners seen from unusual angles. Hands protrude from walls and everyday objects transform into objects of horror.
One of the best-known images is that of a rabbit, which was being prepared for dinner but never cooked. The rabbit sits in the corner of the room throughout the film with a straight razor also on the plate. As the film progresses, the rabbit begins to rot while first maggots and then flies feed on the carcass. The deteriorating state of the rabbit parallels that of our protagonist.
Repulsion is the first of Polanski's "apartment trilogy" (the other two being Rosemary's Baby and The Tenant). As in those two films, the horrors are not external threats, but rather the horrors that lie within the minds of the protagonists.
Music videos for The Cardigans' "Hanging Around" and Metric's "Monster Hospital" were directly inspired by the film.