A Bay of Blood (aka: Twitch of the Death Nerve)

(1971) dir Mario Bava w/Claudine Auger, Luigi Pistilli, Claudio Camaso, Anna Maria Rosati [84 min; DCP]
Acting as his own cinematographer, Bava racked up the body count with this pleasurably convoluted, much-imitated slasher film prototype. When a countess is murdered at her bayside mansion, the crime sets off a chain reaction of killings involving seemingly any and all possible heirs, not to mention a group of teenagers who get caught up in the mayhem. – Quad Cinema