A composer walks in to a crime scene only to find a much overlooked clue, which alludes to the murdered being a serial killer. It is left to him to trace the killer through his life allowing him to discover the motive and location.
The best of Argento's non-supernatural mysteries, this frequently spins off from its Blow-Up-style murder investigation with intimations of magical strangeness.
Composer Hemmings wanders into a Rome flat where a murder has just taken place and glimpses a clue which bothers him for the rest of the film as further, extremely grotesque murders take place. The plot is complicated and takes Hemmings and winning heroine Nicolodi back to a dilapidated infants' school which seems to specialise in junior psychopaths, while the bravura murder scenes encourage the musical accompaniment to go into overdrive. High style horror with occasional black wit.
Undoubtedly the finest of Argento's thrilling horrors, this one takes the radical step, for the director at least, to concentrate on a plot that equals the shocking visuals of his other works. David Hemmings is well cast and is given a great script which genuinely frights.