Most mediocre slasher films choose one or two obvious modelsPsycho or The Texas Chainsaw Massacre or I Spit on Your Grave or Dressed to Kill or Re-Animatorbut this exceptionally gory French item (2003) gropes for all of them and winds up incoherent. The distributor, showing a similar desire to cover all bases, has dubbed some of the dialogue and subtitled the rest. If old-fashioned jolts are what you’re after, this nasty piece of merchandise delivers. But so does electroshock. Alexandre Aja directed; with Cecile de France, Maiwenn Le Besco, and Philippe Nahon. Also known as Switchblade Romance. R, 91 min. (JR)