While it's definatly one of Joe D'Amato's better films, I wouldn't hype "Beyond the Darkness" as his absolute swan song like most. I've always arguably favored "Antropophagus", personally, even though it was basically an extended Coke ad. Still, "Beyond the Darkness" is a fine Italian trash-horror flick and easily one of the film maker's most cinematically compitent works.
A rich young taxidermist's girlfriend dies of some illness, prompting the obessive guy to swipe her corpse from the grave and take her home. Of course, he puts his skills to good use, proceeding to stuff her like you would a animal. He stores her in the bedroom and it's up to the viewer whether or not he's engaging in necrophilic shenanagans... Oddly, homeboy can't seem stop butchering random girls also, such as a stoned out hitch-hiker and an injured jogger. He's assisted by his ever-willing and disturbingly matronly housekeeper who can dismember a corpse for an acid bath without batting an eye. Eventually, he gets in over his head and the cops start snooping around.
Again, some of D'Amato's most ambitious work and full of decent amounts of sleaziness and gore. Corpse butchery, finger-nail extracting, flesh biting. Worth a look.