Inexplicably, Viridiana is ordered by her Mother Superior to visit the estate of her libidinous uncle, Don Jaime, played by Buñuel regular Fernando Rey. She has not seen him in years, even though he paid for her education. Of course, he claims to be dying, and there are family secrets galore in the rich man’s manse. He had a son out of wedlock that he never told his dead wife about, and that wife also died on their wedding night.

Two things can be surmised, even though Buñuel’s script moves so fast and elliptically that a viewer hardly cares about much that occurs early on. The first is that the bastard son will show up in the film (which he does), and the second is that perhaps Jaime killed his wife due to his obvious sexual perversions. He is a closet transvestite and loves female feet — be they Viridiana’s or those of the small girl, Rita (Teresa Rabal), of his servant Ramona (Margarita Lozano).

Another thing that is excruciatingly manifest — the old man’s dead wife looks remarkably like Viridiana. This tired plot point has been used in countless films and soap operas, yet Buñuel is oblivious to its triteness, as he does nothing to subvert the point, nor even burlesque it. Jaime is such a trite creation that when he utters melodramatic lines like, "You must think I’m mad," before proposing to his niece, Buñuel plays it as if it were some great dramatic moment, rather than the naked revelation of this soap operatic film’s true self.

The film moves so quickly that no real sense of any relationship between the old pervert and his niece is built up, yet, literally, just a couple of minutes after she arrives at his estate and tells him it is too late for a relationship, she is telling him (after a stay of a few days) that she has loved her time with him. He, of course, is in love with her, asks her to put on his wife’s wedding dress, and asks her to marry him. She refuses, says she pities him, then he drugs her (with Ramona’s help) and tries to rape her, but cannot go through with it.

Up till that point, the film more closely resembled a Dracula film rather than "serious" drama. He tells her the next morning that he took her virginity and she cannot become a nun. But, his ploy to keep her fails; even after he admits his lie, she goes to the bus station, but before she can leave, Jaime hangs himself, after writing a letter and bizarrely smirking.

He has made her partial heir to the estate, with his son, Don Jorge (Francisco Rabal), a Latin Lothario if there ever was one. He takes over the house with his girlfriend, Lucia (Victoria Zinny), but it is obvious he has the hots for Viridiana, as well as Ramona. He plans on adding electricity and modern amenities to the medieval place. The girlfriend eventually leaves, and Viridiana turns her portion of the estate into a hostel for the poor and ill, after she is mocked for doing so by the callous Mother Superior.