Italian master of horror Dario Argento's second directorial effort (and the centerpiece of the 'animal trilogy' of giallos) is a suspenseful murder mystery infused with the filmmaker's trademark graphic violence. Karl Malden stars as a blind man with a talent for solving puzzles who teams-up with reporter Carlo Giordani (James Franciscus) to launch a private investigation into a string of peculiar murders, all of which seem to involve a dubious genetic research facility. The killer soon becomes wise to the duo's plans and will do whatever it takes to stop them from reporting to the police.