In this flawed mystery-thriller from flamboyant horror director Dario Argento, Karl Malden portrays a blind man who joins forces with a reporter (James Franciscus) to catch a killer with an extra chromosome. Much of the action occurs at a research hospital, where the killer seeks to conceal the original crime with still more murders. Easily the least interesting of Argento's early thrillers (which include the superior L'Uccello dalle Piume di Cristallo and Quattro Mosche di Velluto Grigio), this film seems almost a parody of the genre at times, with preposterous coincidences and bogus Freudian analysis substituting for genuine mystery. Those familiar with the director's work may find it difficult to believe that Argento was responsible, but some undeniable stylistic touches -- such as one victim's wallpaper resembling a blood-splattered wall -- reveal that even a genius can make bad films. Ennio Morricone's soundtrack and a cast including Catherine Spaak and Pier Paolo Capponi offer little relief. The American version is missing approximately twenty minutes.
~ Robert Firsching, All Movie Guide