A university professor returns to Spain, to visit an old friend who now lives with his teenage stepdaughter and second wife. The old friends rediscover the old erotic literature of their youth, and when the daughter discovers it too, she tries to seduce the teacher.
There is one great scene at 1:03:18 where the professor/rare book appraiser is about to have sex with his friend's stepdaughter when her mother (his friend's second wife) knocks on the door of his study/bedroom. While the daughter hides naked in the closet, her clothes hurriedly thrown beneath the bed, the mother seduces the professor. The kinkiest thing is that she sees her daughter's clothes under the bed and probably knows she's in the closet while they're having sex, but doesn't say anything. Then, as soon as the mother leaves, the daughter comes running out of the closet to throw some MORE sex on the guy (for a rare book appraiser, this guy gets more action than Johnny Depp in "The Ninth Gate"--and he's no Johnny Depp). (source: IMDB review)