1995 film by Ninì Grassia

Tourists take a boat to a remote island, where they find that most of the people have disappeared, and something is stalking them. They find a hidden room in the big mansion on a hill, and an ancient diary, which gives them clues to the source of the terror.

The sexual relationship between a successful woman and her brother, an introvert, hypochondriacal youth, who is also a pornophile.