The Nun is a perfunctory hour of pornography from prolific French director Michel Ricaud, hardly above the level of a home movie.
It starts with lovely young nun Anna Petrovna playing organ in church, but peeking at dirty photos torn out of a magazine. She masturbates, with the usual gynecological closeups.
Priest Michel Dupont finds the dirty pictures lying on the organ keys and puts a large dildo next to them, so in the next scene Anna uses it to masturbate again. Hardly scintillating cinema.
Non-story continues with Anna giving the voyeuristic priest a blow-job, having sex with him and then practicing piano, with a slightly older nun having lesbian sex with her.
Anna and Dupont make love again, and the sacrilegious finale consists of the two nuns given the Eucharist wafer by the priest, plus a blow-job.
This is all performed utterly coldly and mechanically, with some "Oui, oui, oui!" moaning dubbed in on the soundtrack. Silliest element is star Anna having tan lines quite visible when she strips -hardly appropriate for her role as a nun (though perhaps libertine nuns may be assumed to engage in sunbathing!).
I recall how Henri Langlois at the Cinematheque Francaise was influential in favoring preservation of all sorts of films, rather than targeting just what was considered significant at the time, but "La Religieuse" by Michel Ricaud might as well be lost, permanently.