Roman Polanski masterfully directs this sort of a variation on the same theme as Repulsion. I can't imagine there is one honest movie goer not able to acknowledge the fine director in Le Locataire, yet both parts of the dyptic may not be thoroughly satisfactory to most people, myself included.

Polanski is very good at making us feels the inner torture of his characters (Deneuve in Repulsion and himself in Le Locataire), starting with some lack of self-assurance soon to turn gradually into psychological uneasiness eventually blossoming into an irreversible physical malaise. The shared ordeal for the characters and audience is really dissimilar from the fright and tension of horror movies since there's no tangible supernatural element here. While horror movies allow for some kind of catharsis (be it cheap or more elaborate) Polanski sadistically tortures us and, if in his latter opus the dark humour is permanent, we are mostly on our nerves as opposed to on the edge of our seats.

Suspense, horror, all this is a matter of playing with the audience's expectations (alternatively fooling and fulfilling them), not literally with people's nerves. In my book Rosemary's Baby is a far greater achievement because sheer paranoia and plain rationality are in constant struggle: the story is about a couple moving in a strange flat, while we are forced to identify with a sole character. What's more if the fantasy elements are all in the hero's mind the situation is most uncomfortable since we, the viewers, are compelled to judge him, reject him while we have been masterfully lured ("paint 'n lure") into being him.