I saw this film in Italian without the benefit of English dubbing or English subtitles (and even without Italian subtitles). Nevertheless, having seen six other Salvatore Samperi films it wasn't too hard to follow it as it develops many of the same themes as his other works--incestuous longings, sexual perversity, dark tragi-comedy, along with an almost overwhelming cinematic stylization and musical score.
Lou Castel plays a teenager who is seemingly physically handicapped, but is perhaps only mentally ill. After enduring a series of shock treatments in the prologue and (seemingly) confined to a wheelchair, he comes to stay with his aunt and uncle (Lisa Gastoni and Gabriele Ferzetti), and an incestuous attraction soon grows between him and the aunt, much to the consternation of the uncle. Castel was a very promising actor in the late 60's whose career was unfortunately derailed by his leftist political leanings. He does a good job here, managing to appear both genuinely mentally disturbed AND charismatically attractive. Ferzetti seemed to get stereotyped in these "twisted Italian family" type films. (In his most memorable film I've seen, he plays a lonely father who gets seduced by his daughter's best friend AND then his own daughter). Gastoni started out in typical voluptuous 60's eye candy roles, but starting with this film, turned into a very daring actress in middle-age (when I'm sure she still never got kicked out of anyone's bed for eating crackers). She and Samperi would team up again for the equally dark and disturbing film "Scandalo".
Samperi meanwhile is perhaps THE most under-appreciated Italian director. I've yet to see one of his films that was legitimately released with English subtitles (as opposed to completely in Italian, horribly dubbed into English, and/or a substandard bootleg). Still, his work is quite interesting. He does have a strange fascination with quasi-incest, but that seemed to be a general thing in Italian films of that era (besides, the Italian actors of that era sure made incest look very appealing . . .). And Samperi adds a twisted ending to this particular "comedy" that I won't give away here, but was probably even more controversial than the incest in Catholic Italy in the late 60's. This is worth seeing, even in Italian.