A virulent strain of ugly and lethal parasites turn the residents of a swanky deluxe apartment complex into depraved sex-crazed fiends. Doctor Roger St. Luc (the hopelessly bland Paul Hampton) and his amiable colleague Rollo Linsky (a wonderfully engaging portrayal by Joe Silver) try to figure out what's going on before it's too late. Writer/director David Cronenberg concocts an unsparingly bleak meditation on the horrors of mankind being reduced to sheer psychotic libido impulses (check out the scene with a homely fat middle-aged woman jumping a younger man while exclaiming "I'm hungry for love!") and does a sound job of creating and maintaining a cold, icky tone which becomes more increasingly creepy and unnerving as the grim narrative progresses towards a wild pull-out-all-the-stops climax which plays like a perverted version of "Night of the Living Dead." The acting is rather hit or miss: Hampton barely registers as the insipid would-be hero, the ever-alluring Lynn Lowry contributes a memorably sexy turn as the enticing Nurse Forsythe, Barbara Steele projects her usual sense of class and commanding presence as poised lesbian Betts, Allan Kolman does well as the infected Nicholas Tudor, and pretty Susan Petrie likewise impresses as Tudor's sweet, distraught wife Janine. Moreover, this picture comes through with several effectively nasty moments: the jolting opening with a deranged old scientist murdering his teenage mistress, cutting opening her abdomen, and pouring acid in her stomach prior to slitting his own throat; Betts being violated by a parasite while taking a bath, a parasite attacking Linsky by attaching itself to his face, and a brief, yet startling shot of two little kids on leashes walking on all fours and barking like dogs. Robert Saad's plain cinematography presents a credible evocation of everyday pedestrian reality while the spare, chilling score does the shuddery trick. Joe Blasco's hideously ghastly and gruesome make-up f/x deliver the disgusting goods. Plus there's a wickedly twisted sense of blithely morbid black humor at work throughout. Not peak Cronenberg, but still worthwhile and engrossing all the same.