Excellent giallo, with just a touch more of the thriller about it than is usual. Direction is assured, camera-work innovative and exciting with all the performances solid, especially the charismatic Mr Nero. The killer does not restrict themselves to women here, for a change, and has a go at men women and children. Fast moving and most entertaining with no pause for any ponderous detective work. Super stylish with amazingly spacious apartments, swirling staircases and contemporary concrete and glass splendour of late 60's Italian architecture. Last but by no means least a lovely understated but truly effective and sparingly used Morricone soundtrack. It's not a lot more than the same enigmatic theme repeated with various orchestrations but it helps the work enormously, as does the splattering of what sound like industrial music and also the silences, especially for the murders, no crashing crescendo, simply unnerving silence. A fave.