|Doesn't get much better than this...
This wonderful Bava creation (an Italian original, and in many ways the blueprint for the later Friday the 13th series) paints the story of a wealthy Countess murdered by her husband and the craziness that begins when a horde of relatives and associates begin to battle for her bayside properties.
Essentially one of the first true slasher films, this stylish "Body Count" granddaddy has numerous, inventive killings that audiences would see duplicated later on in Halloween and the Friday the 13th series.
In addition, some of the plot elements would pop up later in hordes of nameless, faceless slasher flicks. Machetes in heads, spears through gyrating lovers, throats cut while running, etc, etc. All nicely packaged in a somewhat secluded woodsy setting.
Undisputed must see.
Also known as both Twitch of the Death Nerve and Bloodbath.